Category: Chemistry Notes PPT

Alcohols are saturated organic compounds that contain at least one hydroxyl group (OH). The general formula of alcohol is CnH2n+1OH. Alcohol can be of many types. In this article, we will discuss the mannitol. This article will cover all important points like what is mannitol, mannitol structure, mannitol uses, mannitol action and mannitol injection uses. 

What is Mannitol?

Mannitol is a six-carbon, linear, simple, and polyhydroxy sugar alcohol. It is a low molecular weight compound. Its chemical formula is C6H14O6.  It gets easily filtered through the glomerulus but it can not be reabsorbed in the renal tubule of the kidney. 

Mannitol Structure

Mannitol is an isomer of sorbitol. The only difference in the structure of mannitol from sorbitol is the orientation of the hydroxyl group on the second carbon. All the carbons present in the mannitol are sp3 hybridized. All bonds present in the mannitol are sigma bonds.

Comparison of Sorbitol and Mannitol.

Properties of Mannitol

• The molar mass of mannitol is 182.172 g/mol.

• The density of mannitol is 1.489 at 68°F.

• The boiling point of mannitol is 563°F at 3.5 mm Hg.

• The melting point of mannitol is 333°F. 

• It is an odourless compound.

• It occurs naturally in white crystalline or in granule form.

• It is sweet in taste.

Mannitol Action 

• Mannitol is a polyhydroxy compound, which is mildly metabolized by the body. The renal tubule does not have the capacity to absorb it. Therefore, it rapidly gets excreted by the kidney, when mannitol injection is used and poorly absorbed when taken orally.  

• Mannitol, when ingested orally, passes through the intestine and excreted in the feces as the small intestine is not able to absorb it properly. Therefore, it does not affect blood sugar and can be used as a sweetener for the diabetic patient.

Mannitol Uses

• Mannitol is used for promoting diuresis for acute renal failure.

• Mannitol is used for increased intracranial pressure.

• Mannitol is used for the excretion of toxic material.

• Mannitol is used as a sweetener for diabetic food products.

• Mannitol is used for preventing intradialytic hypotension.

• It is used to measure Extracellular Fluid (ECF) and Glomerular Filtration Rate (GFR).

• It is used in cardiopulmonary bypass.

Mannitol Injection Uses

Mannitol is used as a medicine. Mannitol infused into a vein or into the urethra. It should never be given subcutaneously. It is infused by health care professionals in a hospital or clinic. The total concentration, dosage, and rate of mannitol administration should be governed by the nature and severity of the condition. The standard adult dose ranges from 50-200 g/day. The rate of infusion is usually adjusted to maintain a urine flow. 

Harmful Effects of Mannitol

• It can cause dehydration when consumed in excess amounts.

• At low temperature, it gets precipitated and can damage the vascular organ system.

• It can cause heart failure.

• It can cause pulmonary edema.

• It can cause renal failure.

Did You Know?

• Mannitol is found in mushrooms, brown algae, and bark of manna trees.  

• Mannitol lowers the blood pressure. 

• Mannitol in the intestine for a long time can cause bloating and diarrhoea.  

Transition metals are actually the various chemical elements that have valence electrons. It means electrons that can promote the formation of chemical bonds in two shells instead of just one. Although the term transformation does not have any specific chemical meaning, it is a convenient name for distinguishing the similarity of the atomic structures and the resulting properties of the elements. They occupy the center portions of the periodic table of elements between the groups on the left and the groups on the right. Specifically, groups 3 (IIIb) through 12 (IIb)

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What is a Metallic Character? 

According to the metallic character definition, Metallic character refers to the level of the metal’s reactivity. Metals tend to lose electrons in chemical reactions, as implied by their low ionization energy. Metal atoms have a low attraction for electrons within the compound, as indicated by their low electronegativity.

Physical properties related to metallic character involve metallic luster, glossy appearance, high density, high electrical conductivity, and high thermal conductivity. Most of the metals with metallic characters are malleable and ductile and can be deformed without breaking. In this case, Zn, Cd, Hg, and Mn are exceptions. The rest of the elements show one or more metallic characters at room temperature. Except for the metals which are exceptions, the remaining of the elements are hard and have low volatility.

Metallic Character Trend 

According to the modern periodic table, the metallic character of an element decreases as we move from left to right in the periodic table. This is due to the fact that, while moving from left to right in a period of time, the number of electrons and protons in an atom is expected to increase, which makes the nuclear force stronger, and therefore it becomes more difficult to lose electrons.

Metallic character increases down the group. This kind of metallic character trend happens because the atomic radius increases while moving down the group, which makes it easier to lose electrons.

How to Recognize Elements with Metallic Trends?

• Metallic characters are shown by metals, all of which are on the left side of the periodic table.

• The only exception is hydrogen, which is a non-metal under normal conditions. Yet hydrogen behaves like metal when it’s liquid or solid, but perhaps you should perceive it non-metallic for most purposes.

• Metallic elements occur in certain groups or columns of elements, including alkali metals, alkaline earth metals, transition metals (including lanthanide and actinides below the main body of the periodic table), and base metals.

• Other metal categories encompass base metals, noble metals, ferrous metals, heavy metals, and precious metals. Metalloids display some metallic character. However, this family of elements also has some non-metallic properties.

What are Transition Metals?

The metals in the periodic table that mostly consist of the d-block transition elements possessing unique and useful properties are known as transition metals. There are a total of 56 transition elements present in the periodic table which are further classified into three main groups-

There are incomplete inner electron shells in the case of transition metals which act as the transitional links between the most electropositive and least electropositive between the series of elements. The characterization of the transition metals can be done by the points listed below-

Transition Metals – Metallic Character

Transition metals possess low ionization energies and several vacant orbitals are present in their outermost shell. This is the reason behind their metallic character. Typical metallic properties are exhibited by transition metals because of the formation of metallic bonds between them. The presence of covalent bonds is indicated by the hardness that these metals possess which is because they have unpaired d-electrons. The unpaired electrons which are present in the d-orbitals may overlap leading to the formation of covalent bonds.

 

The number of covalent bonds present depends on the number of unpaired electrons. If the number of unpaired electrons is high, the covalent bonds will be formed more. This property leads to an increase in the hardness and strength of the metal. 

The transition metals including chromium, molybdenum, and tungsten are known to be very hard metals because they have the maximum number of electrons present in their d-orbital while on the other hand metals like mercury, zinc, and cadmium are not at all hard since no unpaired electrons are present in their d-orbitals. 

The metallic depends upon the easiness of a metal with which it loses electrons. When we move left to right across the periodic table, there is an increase in the number of protons and electrons which further leads to an increase in nuclear forces on the electrons which makes it difficult for them to lose electrons, therefore the metallic character while moving left to right decreases. As the atomic radius is increased there is an increase in the metallic character as well. Therefore while moving top to bottom, the metallic character of the elements is increased. 

Explanation for the Metallic Character of Transition Elements

• Transitional elements have a metallic character because they have low ionization energies as well as several empty orbitals in their outer shells. Such a property leads to the formation of metallic bonds in transition metals and hence demonstrates common metallic properties.

• These metals are hard, indicating the presence of covalent bonds. This is due to the presence of unpaired d-electrons in transition metals. The d-orbital containing unpaired electrons can sometimes overlap and establish covalent bonds. The higher the number of unpaired electrons present in the transition metals, the greater the number of covalent bonds formed by them.

• The chromium (Cr), tungsten (W) and molybdenum (Mo) metals have a maximum number of unpaired d-electrons. These transition metals are therefore exceedingly difficult. On the other hand, zinc (Zn), cadmium (Cd), and mercury ( Hg) are not extremely hard because they do not have unpaired d-electrons.

Metallic character with Alloys 

Although the metallic character is mainly related to pure elements, alloys could also have a metallic character. For example, bronze and most copper, magnesium, aluminum, and titanium alloys usually show a high level of metallicity. A few other metallic alloys consist purely of metals, but most often contain metalloids and nonmetals, while retaining the properties of metals.

Example Questions 

1. Give some examples of metals that display metallic character 

The metals that display with metallic characters are francium, caesium, sodium, copper, silver, iron, gold, aluminum, etc. Caesium and francium are the elements that display the highest metallic character.

 

2. How does the atomic radius vary in the metallic trends of transition elements? 

The atomic radius increases by going down a group, by moving the outer electrons further away from the nucleus. It makes the electron less attracted to the nucleus. As a result, metals become more reactive as we go down the group.

Michael Reaction Mechanism 

When an α,β -unsaturated carbonyl carbon is treated with a base, the base deprotonates the α,β -unsaturated carbonyl carbon. The deprotonation of α,β -unsaturated carbonyl carbon leads to the formation of an intermediate. The intermediate formed in this reaction is carbanion. The carbanion intermediate consists of a negative charge which can be stabilized by groups that are electron-withdrawing in nature. This reaction was first worked out by an American organic chemist named Arthur Michael and after his name, this reaction is named. This reaction can also be called a nucleophilic addition reaction because the electrons of the base are being donated to a carbon center making it a nucleophile. This reaction is useful because it generates carbon-carbon bonds which is a strong covalent bond. 

Michael Addition Reaction With Mechanism

The nucleophile or base which donates their electron to the proton is called Michael donor. Acyl and cyano groups act as very good nucleophiles because of their non-bonding electrons which are high in energy and are therefore ready to donate. The hydrogen attached to the substrate, methane is acidic and because of that the base or nucleophile readily abstracts it and the carbanion is formed. The substrate where the carbanion is formed is called the Michael donor whereas the other substrate which is attacked by the donor is said to be the Michael acceptor.

 

The reaction is thermodynamically controlled i.e. the product formed will be thermodynamically stable. The Michael donors are mostly active methylene which has electron-withdrawing groups attached to the carbon whose proton is abstracted. The abstracted proton is highly acidic because of the electron-withdrawing group attached to its adjacent carbon as they are capable of stabilizing the carbanion. The Michael acceptors are usually olefins which are electron deficient. 

Example of Compounds Showing Michael’s Addition Reaction

• When diethyl malonate acts as Michael donor and diethyl fumarate acts as a Michael acceptor. 

• Acrylonitrile acts as Michael acceptor and acetylacetone act as Michael acceptor. 

• Malononitrile acting as a Michael donor and ethyl vinyl ether acting as a Michael acceptor. 

Michael Addition Reaction Mechanism

Step 1: 

In the first step, the α -hydrogen is deprotonated by the base which leads to the formation of carbanion. The negative charge on the carbon is stabilized by the carbonyl carbon by resonance as the negative charge on oxygen is more stable than being on the carbon. 

Step 2: 

In the second step, the Michael acceptor being deficient in electrons acts as an acceptor which then accepts electrons from the carbanion which is rich in electrons. The reaction between them forms the carbon-carbon bond. Even though the negative charge is more stable on the oxygen during the resonance structure the carbon-carbon bond is more stable as compared to the carbon-oxygen bond. This is a 1,4- addition reaction. 

Step 3: 

In the third step, the carbonyl compound is protonated by accepting an electron from the solvent which gives us the final product. The reaction mechanism is shown below which shows which bonds were broken during the course and which were formed. 

Mukaiyama-Michael Addition Reaction 

When an organosilicon group (an organic compound attached to silicon) is bonded to the oxygen of an enolate then this functional group is called silyl enol ether and when this functional group acts as a nucleophile in a Michael reaction then that reaction is called Mukaiyama-Michael reaction. The reaction requires titanium chloride to act as a catalyst in the process of forming a new carbon-carbon bond. 

As the title indicates, the molecular structure is the three-dimensional shape or configuration of a molecule. There are several different characteristics that one learns about by looking at the molecular structure definition of a molecule or group of atoms.

It should be noted that the shape of a molecule is also dependent on the preferred spatial orientation of covalent bonds between two atoms that have two or more bonding partners. There are also different dimensional configurations that one can view with the help of a model. These configurations can be represented on paper by using perspective drawing.

In perspective drawing, the direction of the bond is specified by a line that connects both the bonded atoms. There are several types of lines that signify different bonds. Some of those bonds, their lines, and representations are given below.

It is also vital to note here that usually, the focus of a configuration is the carbon atom. This means that the lines specifying the bond directions will all originate from the carbon atom. For example, a straight line from the carbon atom indicates that the bond is approximately lying on the surface plane.

Students should also remember that some textbooks and other sources use a dashed bond in a similar manner to the hatched bond that has been used in this article. If a student ever comes across it, then he or she should not be confused. This is especially true for covalent bonds because those bonds are either partially formed or partially broken.

It is also extremely important for students to show non-bonding valence shell electron pairs in their molecular structures. Missing these electron pairs can create a lot of confusion. For example, the structure of methane, ammonia, and water is almost similar. But the main difference exists in terms of the valence shell electron pairs. This example is also illustrated in the image that is attached below.

                    

              

It is also possible to predict the bonding configurations. This can be done by using the valence-shell electron-pair repulsion theory. This theory is also referred to as the VSEPR theory and it is present in most introductory chemistry courses.

This model is quite simple as it is based on the fact that electrons naturally repel one another. Further, it is also reasonable to expect that the non-bonding valence electron pairs and bonds associated with any given atom will prefer to be as far apart from one another as possible.

At this point, students should remember the bonding configurations of carbon. These configurations are easy to remember and can be classified into three categories. These categories are shown in the table that is given below.

It can also be fun to learn the molecular structure of glucose, the molecular structure of water, and know the difference between molecular structure vs chemical structure.

What are Isomers?

There are compounds that have the same molecular formula but a different structure. These compounds are known as isomers. This is one of the reasons why it is necessary for students to draw the structural formulas for organic compounds.

It should also be noted that the presence of organic isomers reflects the amazing versatility of carbon in forming strong bonds with itself and with other elements. Also, constitutional isomers are compounds that are bonded with each other in fundamentally different ways. These compounds are the group of atoms that make up the molecules of various isomers.

For example, as of now, there are seven constitutional isomers of C₄H₁₀O. The structural formulas for these isomers are also different. It should be noted that there are no double bonds, triple bonds, or rings in any of these structures. Further, each of the carbon atoms is bonded to four other atoms and is saturated with bonding partners.

Fun Facts About the Distinguishing Between Carbon Atoms

Did you know that you can distinguish between different groups of carbon atoms by their structural characteristics? For example, you can find a primary carbon by identifying the one that is bonded to no more than a single carbon atom.

A secondary carbon is the kind of carbon that is bonded to two other carbon atoms. Similarly, a tertiary carbon is bonded to three carbons and a quaternary carbon is bonded to four other carbons. You can also find the three isomers of C₅H₁₂ illustrated below.

             

               

It is also possible for several structural differences to occur within these four groups of carbons. This depends on the molecular constitution. One can also take the consideration of molecular symmetry into account to help distinguish between structurally equivalent and nonequivalent groups and atoms. Also, it is a part of mastering organic chemistry to learn how to distinguish the structural differences and how to draw molecular structure. One can learn this skill through experience and practice.

Natural resources are the resources that exist without any actions or intervention of human beings in nature. This includes all of the valued characteristics like gravitational, magnetic, electrical properties and forces, etc. While talking about Earth, it consists of water, sunlight, atmosphere, land including all minerals along with all the vegetation, crops, and animal life that naturally subsists on or within these known and identified substances and characteristics. 

In this article, we will be learning about natural resources, conservation of natural resources, and the classification of natural resources. Let us first have a look at what natural resources are in detail and how they are conserved.

What are Natural Resources? 

Natural resources are the ones that come from nature. People cannot make natural resources, however, they can collect them. Some of the examples of natural resources include water, coal, wood, and iron. Some of the resources, for example, hydroelectric energy are not considered to be natural since they are made by people.

Classifications of Natural Resources

Let us now look at how natural resources are classified.

Natural resources are mainly classified into 2 different categories:

1. Renewable natural resources and

2. Non-renewable natural resources

Renewable natural resources are the resources that can be generated again once they are used. Some of the examples of renewable natural resources include sunlight, water, and wood.

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Non-renewable natural resources are the ones that exhaust after their frequent usage and sometimes it takes a really long time for them to regenerate. An example of this includes natural gas. Another example of a non-renewable natural resource is coal. Just as coal, there are many such natural resources that are limited which means that they cannot be recycled again. Most of these non-renewable natural resources cannot be recycled and hence it is important to conserve these natural resources. There are several natural resources that have a very high demand but have a lesser availability. 

Difference Between Renewable and Non-Renewable Resources

The main differences between renewable energy resources and non-renewable energy resources are given below.

Examples of the Non – Renewable Natural Resources

Examples of Non- Renewable natural resources are as follows.

1. Air: The existence of all living beings requires clean air. However, due to several reasons, the air gets polluted and it indirectly affects the health of living beings.

2. Water: A very small amount of freshwater is available on Earth. Out of this amount, some amount is portable which means that it can be used for drinking. Since there is a constant change in the climate, there is a change in the rainfall pattern as well. The melting of ice is dropped in winter as well. All these factors result in lowering the amount of this natural resource which is crucial to life on Earth.

3. Fossil Fuels: Natural resources like natural gas, coal, and petroleum would be over someday which means that they are exhaustible. It takes several millions of years for one dead organism to get converted into fuels. They are consumed at a faster rate than the rate that it is formed. The excess burning of these fossil fuels leads to air pollution since it gives out carbon dioxide which is a type of greenhouse gas.

Natural Resources and their Conservation

It is highly important that we conserve these natural resources since they are getting exhausted at an alarming rate. Apart from that, it has an adverse effect on the environment that is indirectly causing harm to living beings. However, if we follow some tips in our day to day lives, we can conserve these natural resources.

1. Use an alternative source of power like solar and wind energy

2. Plant more trees for preventing the soil erosion

3. Use pipelines for transporting oil

4. Treat the industrial sewage and wastage even before they get released into the water bodies

5. Include the rainwater harvesting system in the house

6. Use biogas in the house

7. Use biofuels instead of the conventional petroleum-based fuels

8. Ensure that the wastes are being recycled

9. Use electronic mails

10. Make use of the energy-saving tube lights and bulbs

11. Practice the method of crop rotation

12. Construct reservoirs

Natural Resources and Associated Problems

There are several problems that are attached to natural resources. Let us take a look at them.

1. The irrational consumption and overuse of these natural resources have led to several socio-economic and environmental problems.

2. Natural resources are available in a fixed quantity and are non-renewable.

3. There is an increasing scarcity of these natural resources as the population is increasing day by day.

4. Non-renewable natural resources take millions of years to form.

Conclusion

Hence natural resources are useful and helpful for humans under economical, technological, or social circumstances or supplies drawn from the earth, supplies such as metals, geothermal power water, fertilizers, food, building and clothing materials etc. The article covers all the important basic aspects of natural resources such as their classification, conservation, and associated problems.

Nitrate, named by IUPAC, is a polyatomic ion containing nitrogen and oxygen in it. When a proton is removed from nitric acid, a nitrate ion is formed. The molecular formula of nitrate is NO⁻ ₃. Nitrate ions form salts called nitrates. The conjugate base of nitrate is nitric acid. The structure of nitrate is a nitrogen atom at the center bonded with three identical oxygen atoms. The arrangement of the atoms is in trigonal planar. The formal charge of nitrate ion is -1 because the nitrogen atom carries a charge +1 and each of the three oxygen atoms carries a charge -2/3. These combine with the formal charge of the nitrate ion. Similar to the isoelectronic carbonate ion, the nitrate ion shows resonance. The resonant structures of nitrate ion are shown below

Chemical Properties of Nitrate

• The molecular weight (molar mass) is 62.005 g/mol

• The XLogP3-AA is -1.4

• The number of hydrogen bond donor is 0

• The number of hydrogen bond acceptor is 3

• The number of rotatable bonds is 0

• The topological polar surface area is 62.9 Ų

• The number of heavy atoms is 4

• It has a single covalent bond

• Nitrate ion has no isotope atom

• It has no defined atom stereocenter

• It has no undefined atom stereocenter

• It has no defined bond stereocenter

• It has no undefined bond stereocenter

Conversion of Nitrogen to Nitrate

The conversion of nitrogen to nitrate can be observed in the nitrogen cycle. Single-celled prokaryotes and bacteria trap the atmospheric nitrogen, N2, and converts it through nitrogen fixation into a biologically usable form. These nitrogen-fixing bacteria either live freely in soil and water or, live inside plants as beneficial symbionts. These microorganisms convert the trapped nitrogen and convert them into ammonia, NH3. Plants use this ammonia to make organic molecules. When these plants get eaten up, the nitrogen is transferred to the animals. It is then either excreted by the animal as waste or, incorporated into the body. This nitrogen does not remain in the animal’s body forever. In the end, the organic nitrogen gets converted back into atmospheric nitrogen gas with the help of bacteria. The wastes from animals and decays containing nitrogenous compounds are converted into ammonia by bacteria, which is further converted into nitrite and nitrate. The denitrifying prokaryotes convert the nitrates into atmospheric nitrogen gas, N2. 

Conversion of Nitrite to Nitrate 

The conversion of nitrite to nitrate is observed in a process named Nitrification. It is an aerobic process. When ammonia oxidizes to nitrite biologically and then the nitrite converts to nitrate by oxidation, the process is known as nitrification. One of the most important stages in the nitrogen cycle is nitrification. Nitrification is carried out by archaea and autotrophic bacteria. After the ammonia oxidation, the next step is nitrite oxidation where the bacteria oxidize nitrite into nitrate. Such bacteria are Proteobacteria, Nitrospinae, Chloroflexi and Nitrospirae. These bacteria are found in geothermal springs, soli, marine ecosystems, and freshwater. 

Occurrence and Availability

Nitrates are majorly found on earth as huge deposits of salts, particularly nitratine, which is a source of sodium nitrate. Nitrifying bacteria and other species produce nitrates in the natural environment by using urea and ammonia as a source of nitrogen. By various fermentation processes, urine and dung were also used to produce nitrate and used as gunpowder in historical times. In the atmosphere rich in oxygen and nitrogen when hit with lightning strikes, a mixture of oxides of nitrogen are formed which produces nitrate ions. These nitrate ions are then rained down from the atmosphere. Industrially, nitrate ions are prepared by nitric acid.

Conclusion

Nitrates are found in groundwater and surface levels which generally do not affect our health but if the levels of nitrate are high, it has adverse effects on us. Due to improper well construction, overuse of fertilizers, improper well location, or improper disposal of animal or human waste nitrate levels gets high in well waters. Heating or boiling of the nitrate-rich water will not remove nitrate as due to evaporation of water, water levels in the solution may decrease which in turn makes the solution more concentrated in nitrate. Through chlorination (chemical disinfection) or mechanical filters, nitrate can not be removed from the water. Nitrate treatment processes like reverse osmosis, ion exchange, and distillation can successfully remove nitrate from water.

Do You Know?

1. Few of the identifiers of nitrate are PubChem CID 943, ChemSpider 918, and CAS number 14797-55-8.

2. Nitrates are canonicalized compounds.