Category: Chemistry Notes PPT

Biopolymers are polymers produced from natural sources. These can either be chemically synthesised from biological materials or biosynthesised by living organisms. These are made up of monomeric units bonded together by covalent bonds. These monomeric units form larger molecules. As biopolymers are derived from living organisms like plants and microbes, they are a renewable resource, unlike most polymers which are petroleum-based polymers. 

Generally, biopolymers are degradable. They find use in various industries ranging from food industries to manufacturing, packaging and biomedical engineering. Biopolymers are promising materials owing to their characteristics like abundance, biocompatibility and unique properties like non-toxicity etc. With some nanosized reinforcements to enhance its properties and practical applications, biopolymers are being researched for its use in more and more ways possible.

Examples of biopolymers are protein, starch, cellulose, DNA, RNA, lipids, collagen, carbohydrates etc.

Types of Biopolymers

Biopolymers can be classified according to various scales. These classifications are based on their origin, a number of monomeric units, on the basis of degradability, their heat response etc. Some of the classifications are:

On the Basis of Type

1. Sugar-based polymers- Starch or sucrose is used as input for manufacturing. Lactic acid polymers are created using lactose from potatoes, maise, etc.

2. Starch-based polymers- Starch acts as a natural polymer, composed of glucose. It is found in plant tissues.

3. Cellulose-based biopolymers- Used for packaging, this polymer is made up of glucose obtained from natural sources like cotton. Eg. cellophane.

4. Synthetic materials- Degradable polymers can be made from synthetic materials obtained from petroleum.

On the Basis of Origin

1. Natural biopolymers- These are natural biopolymers biosynthesised by living organisms.

2. Synthetic biopolymers – These are polymers made up of renewable materials like polylactic acid which are degradable.

3. Microbial- Biopolymers produced by microorganisms.

On the Basis of Monomeric Units

1. Polysaccharides-These are carbohydrate chains which are branched or are linear: Eg. starch, cellulose, etc.

2. Proteins- Polymers made up of amino acids. Eg. collagen, fibrin etc.

3. Polynucleotides – Nucleic acids are long polymer chains composed of 13 or more monomeric units. Eg. DNA, RNA etc.

Difference Between Biopolymers and Synthetic Polymers

Applications of Biopolymers

Biopolymers have unique properties and are an abundant material. Due to their unique properties and structures, biopolymers find their application in many places.

Biomedical

Biopolymers are very widely used in the biomedical field. Due to the properties like degradable and non-toxic, biocompatible properties, etc., they are used in tissue engineering, pharmaceutical industry, medicines, drug delivery etc. Polypeptides are inexpensive and easily available, therefore find various uses in biomedical materials. 

Drug delivery systems- Biopolymers like collagen and chitosan are used as drug delivery systems to target the drug and improve drug absorption. Collagen sponges are widely used to treat burn wounds. Both collagen and chitosan are used in tissue engineering. These are very porous and allow the wounds to heal.

Industrial Use

Biopolymers owing to their unique properties find use as industry-standard materials. They are combined with some materials to reinforce the properties of these biopolymers to enhance their desired properties and practical applications. These are widely used in packaging; PHA, polylactic acid and starch being inexpensive and readily available are perfect for this task. They also have barrier characteristics which are not available in other polymers, like these are water-resistant.

Biopolymers are used in the automotive industry to make interior and exterior parts, electrical components, engine, exhaust, steering wheels etc. Biopolymers are added to cement during concrete preparation to increase the desired properties. They are used in the construction industry of interior decoration. Chitosan has properties that remove metals from the water which makes it usable for water purification. Due to its antimicrobial properties, it is also used at places to stop microorganism growth.

Other Applications

• Agricultural/Fishery- Fishing lines, fertilisers, beehives, nets, traps, etc.

• Electronics- In the manufacturing of audio devices, printed circuit boards, insulated wires, cables and other electronic devices.

• Cosmetics – Used for cleaning purposes, pedicure and manicure, also in cosmetic products like sunscreen, hair products, creams etc.

• Sports/Toys- Used to make sports equipment like footballs and other hollow balls, cleats, badminton, golf equipment, etc.

• Nanotechnology- Also used in the production of nanomaterials. Biopolymers have certain unique properties which make them useful in branches of science, for example – the green chemistry. 

Common Biopolymers and their uses

1. Collagen- It is a type of protein which is most abundant in humans (30%). It is made up of amino acids which are further made up of carbon, hydrogen and oxygen. Collagen contains special types of amino acids called Glycine, Proline, Hydroxyproline and Arginine. Collagen gives strength to our various body parts and also protects them. It is a major part of human’s skin and nails. As it is composed of three chains, it has a triple helix like structure. 

2. Gelatin- It is widely used in various industries due to its properties of biodegradability and biocompatibility. Gelatin is a water soluble protein which is derived from collagen (natural polymer). Its main function is to look after the connective tissues such as bones, tenders, cartilage etc. There are 16 different collagen types in the human body. The most prominent ones are the Type I, II and III or collagen I, II and III). 

3. Starch- Starch is one such biopolymer
   which is found in abundance. It is used widely as it is inexpensive, renewable and biodegradable. Starch is a naturally occurring biodegradable polymer which is  easily available from agriculture based activities. People use starch in the food products as well as non food products. 

4. Silk fibroin- It is another type of protein polymer which is obtained from silkworms. It is generally used in fashion textiles and medical stitching. 

Covalent bonds are characterized based on several bond parameters such as bond angle, bond length, bond energy (which is also called bond enthalpy), and bond order. All these bond parameters offer insight into the stability of a chemical compound and the strength of the chemical bonds that hold its corresponding atoms together. Let us discuss more on its important terms like bond order and bond length; bond length and bond energy.

Note: Also, the electronegativity differences of the atoms participating in the chemical bond contributes to the bond energy.

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Bond Order

Bond Order of a covalent bond can be given by the total number of covalently bonded electron pairs between the two atoms in a molecule where it can be found by forming the Lewis structure of the molecule and counting all the electron pair count between the atoms in question.

• Single bonds contain a bond order of 1

• Double bonds contain a bond order of 2

• Triple bonds contain a bond order of 3

It is to note that if the bond order of a covalent bond is given as 0, then the two atoms in question are not bonded covalently (it means no bond exists).

Examples

• The bond order of an oxygen-oxygen bond in the O2 molecule is 2.

• Bond order of a carbon-hydrogen bond of C2H2 (ethyne/acetylene) can be given as 1 to that of the carbon-carbon bond is 3.

• In a carbon monoxide molecule, the bond order of carbon-oxygen is given as 3, where the illustration in the Lewis structure is given below.

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• As the nitrate ion is stabilized by the resonance, the bond order of the nitrogen-oxygen bond is given as either 1.33 or 4/3. It is calculated by dividing the total nitrogen-oxygen bond count (4) by the total covalently bonded nitrogen-oxygen group count (3).

Bond Order, Based on the Molecular Orbital Theory

According to the molecular orbital theory, the covalent bond’s bond order is equal to half of the difference between the bonding electrons and antibonding electrons count, which can be represented using the formula given below.

Bond Order = (½) * (total number of bonding electrons – total number of antibonding electrons)

Bond Angle

We can define the bond angle as the angle formed between the two covalent bonds that originate from a similar atom. A detailed illustration of the bond angle in a water molecule (104.5 °C) is depicted below.

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The Bond Angle can be referred to as the geometric angle between any two adjacent covalent bonds. At the same time, this bond parameter provides insights into the compound’s molecular geometry.

Define Bond Length?

Bond length can be given as a measure of the distance between the nuclei of two chemically bonded atoms present in a molecule. Approximately, it is equal to the sum of the two bonded atom’s covalent radii. For the covalent bonds, the bond length is inversely proportional to the bond order, whereas the higher bond orders result in stronger bonds, accompanied by the stronger forces of attraction that hold the atoms together. In contrast, short bonds are the consequence of these strong attraction forces. The bond length formula can be given as r1+r2.

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The description of the bond length illustration of a covalent bond concerning the sum of the covalent radii individual of the participating atoms is represented above. Experimentally, this bond parameter can be determined with the techniques given below:

• X-ray diffraction

• Rotational spectroscopy

• Neutron diffraction

The bonded atoms tend to absorb the thermal energy from their surroundings and vibrate constantly. This vibration further causes the bond length to differ. Thus, it is very important to make a note that the bond length of a covalent bond describes the average distance between the nuclei of the participating atoms.

Periodic Trends in Bond Length

The bond lengths are always directly proportional to the atomic radii of the participating atoms. The periodic trends that are observed in the bond lengths of elements are the same as the periodic trends present in the atomic radii of the elements (increases down the group and decreases across the period).

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A detailing illustration of the periodic trends in bond length is given above. It can also make a note that the H-H bond is the shortest bond length having 74 picometers.

Bond Enthalpy or Bond Energy

Bond Enthalpy is given as a measure of the strength of a chemical bond. It can also be defined as the energy needed to break all the covalent bonds of a specific type in one mole of a chemical compound (which exists in its gaseous state).

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It is also important to make a note that the bond energy is not similar to the bond dissociation energy. The latter is the enthalpy change associated with the homolytic cleavage of a bond, whereas the former is the average of the bond dissociation enthalpies of total bonds (of a particular type) present in a molecule.

Factors Affecting the Bond Energy

The chemical bond’s strength is directly proportional to the amount of energy needed to break it. Thus, bond energy is given as follows:

• Directly proportional to the bond order; that is, multiple bonds contain high bond energies.

• Inversely proportional to the bond length, that is, longer bonds contain lower bond energies, and

• Inversely proportional to the atoms’ atomic radii, participating in the bond (because the atomic radius is directly proportional to bond length).

Bromothymol blue is also called bromothymol sulfonephthalein, and BTB, which is a pH indicator. It is mostly used in applications that hold measuring substances that would have a neutral pH (nearly 7) relatively. As a common use, we can say it for measuring the presence of carbonic acid in a liquid. It is typically sold in its solid form because of the sodium salt of the acid indicator. 

The other names of Bromothymol Blue can be given as 3,3′- Dibromothy molsulfon phthalein and Di Bromothymol Sulfo Phthalein.

Bromothymol Blue Formula

Bromothymol blue is a relatively large molecule and has a weight of 625 g/mol. The chemical formula of this compound comes out to be C₂₇H₂₈Br₂O₅S. Bromothymol blue has a unique structure that consists of three aromatic benzene rings. The first benzene ring has a thym group connected to it along with a sulfur atom that has two oxygen atoms bonded to it via double bonds. Another oxygen atom is attached to the sulfur atom via a single bond. The second and third benzene rings each have a bromine atom, an alcohol group, a tert-butyl group, and a methyl group attached.

The name ‘bromothymol’ is the common name of the compound. The most scientifically accurate naming system is the IUPAC nomenclature. The IUPAC name of this compound is 4, 4 – (1, 1 – Dioxide-3H-2 , 1 – benzoxathiole – 3 , 3-diyl ) bis ( 2 – Bromo – 6 – isopropyl – 3- methyl phenol.

Bromothymol Blue Structure and Properties

Bromothymol blue is the indicator that acts as a weak acid in a solution. Thus, it can be either in a deprotonated form or protonated form, by appearing blue or yellow, respectively. It is also a bright aquamarine by itself and greenish-blue in a neutral solution. This neutral form deprotonation results in a structure highly conjugated, considering the color difference. A deprotonation intermediate mechanism is responsible for the greenish color in the neutral solution.

The bromothymol blue’s protonated form has its peak absorption at 427 nm, therefore transmitting yellow light in the acidic solutions. 

In contrast, the deprotonated form contains its peak absorption at 602 nm, thereby transmitting the blue light in many basic solutions. Besides, the Bromothymol blue which is highly acidic is magenta.

The bromothymol blue’s general carbon skeleton is common to most of the indicators, including thymol blue, bromocresol green, and chlorophenol red.

The presence of a single moderate electron-withdrawing group (which is a bromine atom) and two moderate donating groups (which are alkyl substituents) are completely responsible for the active indication range of bromothymol blue from a pH value of 6.0 to 7.6. While the conjugation is responsible for the nature of the color change range and length, these substituent groups are ultimately responsible for the active range of the indicator.

Bromothymol blue indicator is sparingly soluble in oil but soluble in ether, water, and alkalis’ aqueous solutions. It is also less soluble in nonpolar solvents, including toluene, benzene, and xylene, and it is practically insoluble in petroleum ether.

Physical Properties of Bromothymol Blue

Let us look at some of the physical properties of bromothymol blue.

Odor- Odorless

Covalently – Bonded Unit 1

Appearance – Yellow – in acidic solutions; green – in neutral solutions; blue – in basic solutions Bromothymol blue ph. 

Synthesis and Preparation

We have already studied how bromothymol blue is a large molecule that consists of three benzene rings. These aforementioned benzene rings have two bromine atoms, one sulfur atom, and an alcohol group connected to them. In its true form, bromothymol blue is a powder. This makes it difficult to mix it in with the sample for pH testing. This is why we try to first convert the compound into an aqueous solution.

Reagents required for this process:

Steps involved in the process: 

Calculations:

If you follow the measurements given above, you will make a 0.04% bromothymol blue solution. The entire solution has a volume of 250 mL, and there is 0.1 g of bromothymol blue in the solution. 0.1 divided by 250 is equal to 0.0004 or 0.04%. 0.04% is the most common concentration used here but 0.01% is also used sometimes. To make the solution change to a concentration of 0.01%, all you need to do is increase the amount of water you add. Then, proceed with the calculations in the manner demonstrated below:

0.1/x = 0.0001

0.1 = 0.0001x

0.1/0.0001 = x

Thus, x is equal to 1000. 

Bromothymol blue is synthesized by adding elemental bromine to the thymol blue in a solution of glacial acetic acid.

To prepare a solution that is used as a pH indicator, we should dissolve 0.10 g in an 8.0 cm³ N/50 NaOH and then dilute it with water to 250 cm³. To prepare a solution used as an indicator in volumetric work, we should dissolve 0.1 g in 100 cm³ of 50% (v/v) ethanol.

Uses of Bromothymol Blue

Let us discuss the major uses of bromothymol blue in detail.

Bromothymol blue can be used either to observe photosynthetic activities or as a respiratory indicator (which turns yellow as CO₂ is added). A common demonstration of the pH indicator properties of BTB involves exhaling through a tube into the neutral solution of Bromothymol blue. As the carbon dioxide is absorbed from the breath into the solution, the solution changes its color to yellow from green by forming carbonic acid. Therefore, BTB can be used commonly in science classes to demonstrate that, “the more that the muscles are used, the greater the carbon dioxide output.

Bromothymol blue indicator has been used in conjunction with phenol red in monitoring the fungal asparaginase enzyme activity, with the phenol red turning pink. And, the bromothymol blue turns blue by indicating an increase in pH and thus enzyme activity. However, one recent study suggests that the methyl red part is more useful in determining the activity because of the bright yellow ring form in the enzyme activity zone.

It can also be used in the laboratory as a stain of a biological slide. It is already blue at this point, and a few drops are used on the water slide. The coverslip is also placed on the top of the water droplet, including the specimen in it, mixed with blue coloring. Sometimes, it is also used to define nuclei or cell walls under the microscope.

Bromothymol can be used in obstetrics for detecting the premature rupture of membranes. Typically, the amniotic fluid has a pH value of greater than 7.2, and the bromothymol will thus turn blue when made in contact with the amnion’s leaking fluid. Normally, as the vaginal pH is acidic, its blue color indicates the amniotic fluid’s presence. The test may result in false positives in the presence of other alkaline substances, including semen or blood, or the presence of various bacterial vaginosis.

Chronic Effects of Bromothymol Blue on Humans: 

Bromothymol Blue causes damage to the organs, including mucous membranes, lungs.

Multiple Adverse Effects on Humans:

It is very dangerous for ingestion, inhalation, and skin touch (irritant).

Caffeine may be a bitter and white crystalline purine that is a methylxanthine alkaloid and is chemically associated with the adenine and guanine bases of desoxyribonucleic acid and RNA. It is found within the seeds, fruits, nuts, or leaves of a variety of plants. These plants belong to a native of Africa, East Asia, and South America. These help to guard them against herbivores and from the competition by preventing the germination of nearby seeds. It also encourages consumption by select animals like honey bees. 

The best-known source of caffeine is the coffee bean, the seed of the coffee plant. People may drink beverages containing caffeine to alleviate or prevent drowsiness. To make these drinks, caffeine is extracted by steeping the plant product in water, through a process called infusion. Caffeine-containing drinks, like coffee, tea, and cola, are consumed globally in high volumes. In 2020, almost 10 million tonnes of coffee beans were consumed globally.

The world’s primary source of caffeine is the coffee berry, from which coffee is brewed. The caffeine content in coffee varies widely depending on the type of coffee bean and the method of preparation used. Generally, dark-roast coffee has less caffeine than lighter roasts because the roasting process reduces the bean’s caffeine content. Arabica coffee normally contains less caffeine than the robusta variety.

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Caffeine Structure and Chemical Formula

Caffeine is a methylxanthine alkaloid that is found in the seeds, nuts, or leaves of a number of plants native to South America and East Asia. These are structurally related to adenosine and act primarily as an adenosine receptor antagonist with psychotropic and anti-inflammatory activities. Upon ingestion, caffeine binds to adenosine receptors in the central nervous system, which inhibits adenosine binding. Stimulating the activity of the medullary, vagal, vasomotor, and respiratory centres within the brain. This agent also promotes neurotransmitter release that further stimulates the CNS. The anti-inflammatory effects of caffeine are due to the inhibition of the intracellular concentration of cyclic AMP (cAMP), which activates protein kinase A. It also inhibits leukotriene synthesis, which results in reduced inflammation and natural immunity.

Caffeine Chemistry is as Follows:

Caffeine IUPAC name is as follows 1, 3, 7-Trimethylpurine-2,6-dione, is an organic compound that is part of the list of the Most Essential Medicines of the WHO. It is also part of the much-extended drink coffee and is a very popular stimulant. The caffeine chemical formula is C[_{8}]H[_{10}]N[_{4}]O[_{2}] and its molar mass is 194.19 g mol[^{-1}].

Caffeine Chemical Structure

The molecule may be a typical natural alkaloid that is formed by a pyrimidinedione consisting of a six-member ring with two nitrogen atoms. And an imidazole is a five-member ring with two nitrogen atoms rings that are fused. Its chemical structure is often written as below, within the common representations used for organic molecules.

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Caffeine Physical and Chemical Properties

Physical Properties: Caffeine molecules are usually obtained from different plants which are cultivated thereupon purpose. It is calculated that tea or coffee leaves contain a maximum of five% of caffeine. The caffeine is isolated by extraction using organic solvents and through the process of a high-pressure extraction, it’s obtained a maximum possible quantity of caffeine. There are a couple of methods to organize caffeine in chemical laboratories. These methods include the reaction between dimethylurea and malonic acid.

Chemical Properties: Caffeine may be a stimulant of the central nervous system. It is suspected the mechanism of action involved reversibly blocks the action of adenosine in some receptors and thus, it stimulates the nervous system. The caffeine molecule can act this way because the molecule structure is very almost like an adenosine molecule, particularly on the part like the nitrogen base adenine.

Caffeine Molecule Side Effects

• When taken by mouth, caffeine is safe for most healthy adults when used in doses of up to 400 mg per day. This amount of caffeine is analogous to what’s found in about four cups of coffee.

• Caffeine is possibly unsafe when taken by mouth for a long time or in high doses supposedly greater than 400 mg per day. Caffeine can cause insomnia, nervousness and restlessness, stomach irritation, nausea, increased pulse and respiration, and other side effects. Larger doses might cause headaches, anxiety, agitation, and pain.

• Caffeine when taken orally in very high doses can cause health issues because it can cause irregular heartbeats and even death. Products with very concentrated or pure caffeine have a high risk of getting used in doses that are too high. So, one should avoid using these products.

• Bipolar disorder, by the excessive amount of caffeine consumption that might make this condition worse. In one case, a 36-year-old man with controlled manic depression was hospitalized with symptoms of mania. After drinking several cans of an energy drink containing caffeine, taurine, and other ingredients over a period of four days. Use caffeine with care and in low amounts if you’ve got manic depression.

• There is concern that caffeine might aggravate bleeding disorders. Use caffeine with care if you’ve got a bleeding disorder.

• Caffeine can increase the quantity of calcium that can be flushed through urine. If one has got osteoporosis or low bone density, caffeine should be limited to but 300 mg per day. If a person is generally healthy and getting enough calcium from food or supplements, then in such persons taking over 400 mg of caffeine per day doesn’t seem to increase the risk of getting osteoporosis. Older women with a genetic disease that affects the way vitamin D is employed should use caffeine with caution. Vitamin D works with calcium to build bones.

Conclusion

Caffeine may be a stimulant of the central nervous system of the methylxanthine class. It is the world’s most generally consumed mind-altering drug. There are several known mechanisms of action to elucidate the consequences of caffeine. The most prominent is that it has the capability to reversibly block the action of adenosine on its receptors. Consequently, it can also prevent the onset of drowsiness that is induced by adenosine. Certain portions of the autonomic nervous system can be stimulated by caffeine.

A Canal ray (also known as a positive or anode ray) is described as a positive ions’ beam, created by certain gas-discharge tube types. These rays were observed in 1886 in Crookes tubes when the German scientist named “Eugen Goldstein performed experiments.” 

Later on, anode rays work by the scientist Wilhelm Wien and J. J. Thomson led to the mass spectrometry development. So, it is said that Dempster is the one who discovered canal rays. He was also one of the first spectrometers to use such ions’ sources.

Canal Ray Experiment

The canal rays experiment is the one that led to the discovery of the proton. The proton discovery has happened after the electron discovery has further strengthened the structure of the atom. In this experiment, Goldstein happened to apply a high voltage across a discharge tube that had a perforated cathode. Also, a faint luminous ray was seen extending from the holes of the back of the cathode.

Apparatus of the Experiment

The apparatus of this experiment includes the same cathode-ray experiment, made up of a glass tube containing two metal ion pieces at different ends that acts as an electrode. These two metal pieces are further connected with an external voltage. The air evacuation lowers the pressure of the gas present inside the tube.

The Procedure of the Experiment

Let us discuss more details about the procedure of the experiment, as listed below.

• As the apparatus is set up by evacuating the air and giving a high voltage source for maintaining a low pressure inside the tube.

• The high voltage is passed to the two metal pieces to ionize the air by making it an electricity conductor.

• Thereby, the electricity starts to flow as the circuit is complete.

• When the voltage was increased to thousands of volts, a faint luminous ray was seen, extending from the holes present behind the cathode.

• These rays moved in the opposite direction facing the cathode rays and were called canal rays.

Explanation

When a higher voltage is applied, the experiment ionizes the gas, and it is the positive ions of gas that constitute the canal ray. It is the kernel or nucleus of the gas that is used in the tube, and thus, it has different properties to that of the cathode rays, made up of electrons.

Differences between Cathode and Anode Rays

Basically, in the first Canal ray experiment, William used the Crookes tube supplying high voltage and gradually reduced the pressure within the tube chamber from 0.01 to 0.001 atm. Also, he noticed a certain beam of light starting to emanate from the tube’s cathode, and this travelled throughout the tube upon reducing the pressure further.

Then, the light emitted from the ray was passed via the strong electric field formed between two plates, charge positive and negative. The light beam was found to curve towards the positive plate and was thus charged negatively. It was named Cathode Rays because it originated from the Cathode of the Tube.

After that, using a perforated Cathode (Cathode with fine pores), he conducted another experiment. Even this time, too, he saw the light, but now, starting from the middle of the tube. Upon increasing the voltage and reducing further pressure, the beam went towards the cathode. The beam bent towards the negative plate when the light beam was placed in between an electric field, and hence, these rays were charged positively.

But we cannot call them Anode Rays since they weren’t emitted from the AnodeAnode. Therefore, they were known as Canal Rays because they formed light ‘canals’ when they left the cathode’s perforations.

Production of Anode Rays

When a high range of voltage is applied to the tube, the electric field accelerates the small ions count (electrically charged atoms) that are always present in the gas, created by natural processes like radioactivity. These collide with the gas atoms by knocking the electrons off of them and creating added positive ions. These electrons and ions strike more atoms, in turn, creating added positive ions in a chain reaction. Then, all the positive ions get attracted to the negative cathode, and a few of them pass through the holes in the cathode if any. These are known as the anode rays.

Conclusion

• Unlike the cathode rays, canal rays will depend upon the nature of gas that is present in the tube. This is due to the canal rays being composed of positive ionized ions formed by the ionization of gas present in the tube.

• The charge to the ratio of mass for the ray particles was different for different gases.

• The particle’s behavior in the magnetic and electric fields was opposite compared to the cathode rays.

• Besides, a few particles that are charged positively carry multiples of the fundamental value of the charge.

• E. Goldstein also concluded that apart from the cathode rays that pass from the negatively charged electrode to the positively charged electrode, there is another set of rays that move exactly in opposite directions which is from a positively charged electrode to a negatively charged electrode and these rays are canal or anode rays. They were further analyzed and it led to the discovery of a positively charged subatomic particle called “Proton”. 

Carbon Tetrachloride is a chemical that does not occur naturally. It is manufactured in the form of a clear liquid that can be detected at low levels. It is prepared by the chlorination of several hydrocarbons of low molecular weight. These include carbon disulfide, methane, ethane, and propane. It can also be prepared by thermal chlorination of methyl chloride. 

 

Carbon Tetrachloride is an important chemical and has several industrial uses. If you are a student of Chemistry, you must understand the properties, structure, and application of this chemical well. 

 

In this article, you will get familiar with Carbon Tetrachloride, its structure, its properties, potential sources, and applications. You will also read about the potential threat one can face if exposed to this chemical for a prolonged duration. Refer to the official website of or download the app for a detailed and comprehensive explanation.

 

What is Carbon Tetrachloride?

Carbon tetrachloride is also called tetrachloromethane, which is an organic compound. The carbon tetrachloride formula is CCl4. The CCl4 molecule is often classified as a polyhalogenated organic compound because it consists of a carbon atom that is attached to more than one halide functional group. 

For pressure and temperature under standard conditions, CCl4 exists as a colourless liquid that emanates an odour of very sweet. The CCl4 chemical name can be given as Carbon Tetrachloride. Earlier, this compound was used widely in cleaning agents. Also, it is used in fire extinguishers and is known to serve as a precursor to various refrigerants.

 

Point to Note: This compound usage has been phased out by various governments because of its toxicity. A large quantity of carbon tetrachloride inhalation can cause serious damage to vital organs such as the liver and kidney. It can also exhibit negative effects on the CNS (Central Nervous System). Moreover, prolonged human exposure to carbon tetrachloride often leads to death.

 

Nomenclature

Carbon Tetrachloride is given the IUPAC name 1,1,1,1-tetrachloromethane. This name is given because the central atom is carbon and it is surrounded by the functional groups of four chlorine atoms.

 

Carbon Tetrachloride Explained

This compound was also used widely as a precursor to chlorofluorocarbons (CFCs). However, since the 1980s, the production of this compound has seen a sharp decline because of environmental concerns. Exposure to carbon tetrachloride can cause centrilobular hepatic necrosis. This compound is metabolized in our body into the trichloromethyl radical, which is highly reactive and can cause hepatocellular damage.

 

Structure of a CCl4 Molecule

Carbon tetrachloride molecules contain tetrahedral molecular geometry, where the central carbon atom is bonded to 4 chlorine atoms. The structure of CCl4 molecules can be illustrated as follows.

 

It makes a note that the 4 chlorine atoms are symmetrically positioned at every corner around the central carbon atom of the CCl4 molecule. The bonds between the chlorine and carbon atoms are covalent. It exhibits non-polar properties as a consequence of the molecular geometry of this compound. It is also noted that the molecular structure of CCl4 is quite the same as that of CH4 (methane gas).

 

Sources and Potential Exposure

• Individuals can be exposed to carbon tetrachloride compounds in the air from accidental releases from uses and production. It can be evaporated into the leach or air into groundwater from its disposal in landfills.

• It is a standard contaminant of indoor air; exposure sources appear to be products, including cleaning agents, used in the home or building materials.

• Workers who are involved directly in the use or manufacture of carbon tetrachloride are most likely to face significant exposures to carbon tetrachloride.

• Individuals can also be exposed to CCl4 molecules by drinking contaminated water.

 

Properties of Carbon Tetrachloride

Let us look at a few important physical properties and chemical properties of the CCl4 molecule, as listed below:

• The molar mass of carbon tetrachloride molecular weight is given by 153.81 gms per mole.

• This compound exists in the liquid state under standard conditions. It has a sweet odour and colourless appearance.

• This compound’s density in its liquid state corresponds to 1.5867 gms per cubic centimetre.

• The melting point of this molecule is given as -22.93 ⁰C, whereas the boiling point corresponds to 76.72 ⁰C.

• The CCl4 molecule is not very soluble in water. The solubility of carbon tetrachloride at a temperature of 25 ⁰C in water is only 1 gram per litre (approximately). However, it should note that this compound is soluble in various organic solvents, including benzene, chloroform, ethers, alcohols, and formic acid.

• Carbon tetrachloride also crystallizes in a monoclinic crystal lattice.

• The coordination geometry of this molecule contains a tetrahedral shape, and the molecular shape is also tetrahedral. It can also be noted that carbon is the central atom in this scenario.

• The thermal or heat capacity of carbon tetrachloride is 132.6 Joules per mole-Kelvin.

• The standard molar entropy that is associated with this organic compound is given by 214.42 Joules per mole Kelvin.

 

Key Applications of Tetrachloromethane

Prior to the 1980s, the carbon tetrachloride compound’s primary application was in the chlorofluorocarbons production for refrigeration. It was also used as a good component of a cleaning agent and fire extinguishers. However, the health hazards that are associated with this compound, including the serious environmental damage caused by chlorofluorocarbons, have been phased out by the governments of various countries. 

 

However, the compound is known to have other niche uses, where a few of them are listed below:

• Carbon tetrachloride compounds can be used as a chlorine source in a named reaction, called Appel reaction.

• It is also used to reveal watermarks placed on stamps without damage to the stamp in the process.

• This compound was also used as a component in lava lamp manufacturing.

• Historically, the CCl4 molecule has been used in NMR spectroscopy of the proton.

 

Health Hazards Associated with Carbon Tetrachloride

Carbon tetrachloride can be dangerous to health depending on the following factors:

• How often is a person exposed to Carbon tetrachloride?

• How much of the substance was ingested by someone?

• How long was the person exposed to Carbon tetrachloride?

 

Depending on these factors Carbon tetrachloride can have serious effects on a person’s liver, kidney and nervous system. 

 

There are various ways in which a person can be exposed to Carbon tetrachloride. These include drinking, breathing its vapours or going in through a person’s skin.

 

Carbon tetrachloride compound is a highly potent hepatotoxin that can cause serious liver damage. Also, this compound can damage the central nervous system (CNS) in high enough concentrations. 

 

Exposure to the CCl4 molecule for a prolonged duration often leads to coma or even death, and it has also been linked to kidney and cancer damage, sometimes.

 

How to avoid Carbon tetrachloride poisoning?

Although it is not likely to get exposed to large amounts of Carbon tetrachloride outside the places where it is manufactured due to the strict regulation of the chemical, people may get exposed to smaller amounts at homes. To avoid being exposed to Carbon tetrachloride in any amount:

• Check the labels of household products and look for safer chemical-free alternatives.

• Keep any dangerous chemical out of the reach of kids. 

• Any products containing Carbon tetrachloride used in the past must be discarded safely.

• If you are a worker at a Carbon tetrachloride manufacturing plant, make sure you wear the required protective equipment including masks, gloves and protective clothing all the time.

• Make sure all the products being used are correctly labelled. To avoid any confusion, store potent chemicals in their original containers.

• Carbon tetrachloride is a dangerous chemical and care must be taken at all times if dealing with such a chemical at any point. Prevention and safety are extremely important to avoid any disastrous effect on our health and of everyone else.

 

Symptoms of Carbon tetrachloride Poisoning:

Short term exposure to Carbon tetrachloride can cause headache, dizziness, lethargy, weakness, nausea, and vomiting. However chronic exposure can cause serious damage including death as mentioned previously. 

 

Treatment for Carbon Tetrachloride Poisoning:

Unfortunately, there is no sure shot treatment for Carbon tetrachloride poisoning. The course of treatment usually depends on the type of exposure. 

 

In case Carbon Tetrachloride gets in your eyes, wash your eyes well for a good amount of time and seek medical attention right away. If the chemical gets on your skin, immediately get rid of the contaminated clothes and wash the affected area thoroughly with soap. Also, seek immediate medical help. Medical help must be sought immediately if you inhale or swallow Carbon Tetrachloride.