Category: Chemistry Notes PPT

Nitric acid is commonly known as aqua fortis or spirit of nitre. It is represented by the chemical formula of HNO3. It is a very strong oxidizing agent and a super-strong corrosive mineral acid. It is a colourless acid but older samples will acquire a yellow cast due to the formation of oxides of nitrogen. Commercially available nitric acid is concentrated up to 68% w/w. This means that 68 grams of nitric acid are dissolved in 100 ml of water. 

Nitric acid is an important laboratory reagent used for nitration- the addition of the nitro group to an organic molecule. There are other varied uses of nitric acid in the industrial sector. Talking about its chemical structure, nitric acid is an example of a monobasic acid.

Formula: HNO₃

What is the Nitric Acid Density, Boiling Point and Melting Point? 

• Density: 1.51 g/cubic cm

• Boiling point: 83℃

• Melting point: -42℃

Areas of Application of Nitric Acid

There are many important uses of HNO3.  These are as follows-

• In fertilizers: Nitric acid is a very important compound used in the production of different kinds of fertilizers. Nitrogenous fertilizers are one of the main categories of fertilizers for example calcium nitrate, ammonium nitrate, etc. Nitric acid is used to manufacture these compounds. Nitrogen is one of the primary nutrients that is required by plants. It plays a very crucial role in plant physiology and hence plants require an excessive amount of nitrogen as compared to other elements. Hence nitrogenous fertilizers are of vital importance to agriculture and farming.

• The precursor to nitro organic compounds: Nitric acid is used for the nitration of several organic compounds. The nitro group is a very versatile functional group by which many explosives such as TNT is prepared. This group is added to aromatic compounds by using a mixture of nitric acid and sulfuric acid. 

C6H5CH3 + 3HNO3 🡪 C6H2(NO2)3CH3+ 3H2O

The above mentioned is the chemical equation for the preparation of the explosive TNT.

• Polymer synthesis: Nitric acid is the raw material for the synthesis of many chemical compounds. Polymers like polyamines and polyurethane are few compounds that essentially require nitric acid for their synthesis. Certain polymerization reactions take place only in presence of a nitric acid medium. 

• Rocket propellant: Nitric acid is used as a rocket propellant in the aerospace industry. This form of nitric acid is known as the red fuming nitric acid which is a storable oxidizer. It contains 84 % nitric acid, 13% dinitrogen tetroxide and 1 to 2% of water.

• As an oxidant: Nitric acid is a very strong oxidizing agent hence used as an oxidant. Adipic acid which is a precursor to the polymer nylon is produced on a very large scale by the oxidation of KA oil which is a mixture of cyclohexanone and cyclohexanol by nitric acid. The function of nitric acid here is to oxidize the oil to yield adipic acid. 

• Manufacture of various industrial products: Nitric acid is used for the production of various industrial products like nitrate salts, dyes, coal tar products, various drugs.

• In preparation of aqua regia: Aqua regia is a yellow fuming liquid made by mixing concentrated nitric acid and concentrated hydrochloric acid in ratio 1:3. It can dissolve noble metals like gold and platinum hence it is used in the purification of gold and platinum and also in jewellery making. 

• Nitric acid uses at home: Directly nitric acid is not used in our daily life owing to its extreme power of corrosion and harmful effects on human tissue. Instead, the products manufactured from nitric acid like various medicines, cleansers, fertilizers for the garden are used in our homes on a daily basis. Uses of nitric acid in our daily life can be said as a laboratory school reagent. Dilute nitric acid is used in the woodworks and carpentry to fabricate a maple and pine wood log for giving them an old look. Nitric acid is used in the spot test of alkaloids like LSD which is known as the colourimetric test.

• Nitric acid medical use: Nitric acid is used to prepare homoeopathic medicines through a process called potentization. There are drugs that cure throat sore and tonsillitis, mouth ulcers, piles and skin issues.

Interesting Facts About Nitric Acid

Nitric acid is produced by the process called the Ostwald process. This was discovered during the time of the first World War and was a reason behind the extension of the war. This was because Germany had no method of producing nitric acid which was essential for the production of explosives used in the artillery shells like nitroglycerin and nitrotoluene. Nitrates are available only from Guano islands in the form of droppings of fish-eating birds. Hence another method to make nitric acid was essentially required.

Nitric acid is an extremely corrosive acid and can cause irreparable burns on the skin. It burns the human tissue. It should be handled under expert supervision at school or other places. It should be kept out of reach of students. The concentrated form of the acid is usually not used for demonstration in schools as it is more corrosive as compared to the dilut
e form.

Water is a transparent, tasteless and odourless liquid that is essential for all living beings. Water has several distinct properties that are important for the sustenance of life. It is important as a solvent that helps dissolve all the solutes of the body and facilitates several metabolic processes within the human body. There are several uses of water in daily life. It helps to flush out the toxins from our bodies. It plays a critical role in photosynthesis and is released during respiration. 

Around 70% of the earth’s surface is covered with water. However, only a small percentage (around 1%) of it is suitable for human consumption. There has been an exponential rise in the global population while the supply of water has remained fairly constant. Some of the sources of water like rivers and lakes are getting contaminated due to industrial pollution and poor policymaking. 

Oceans and the frozen areas of the polar region hold a large portion of the global water content. The water cycle is a phenomenon where the water vapour created from oceans, lakes, and rivers condenses and returns to the earth through precipitation. The cycle includes evaporation, precipitation, and runoff as the transfer processes. Ponds, lakes, rivers, streams, and seas are some of the sources of water which depend on rains and the water cycle. 

Human beings need water for hydration as we regularly lose water during breathing, sweating and digestion. The amount of water that is needed depends on the climate, kind of physical activity and health status of the individual. Other living beings are equally dependent on water for their survival. For plants, the moisture content of the soil helps them to grow. 

Characteristics of Water:

• Some of the characteristics of water are:

• It is a polar inorganic compound.

• The water molecule contains 2 hydrogen atoms and 1 oxygen atom. 

• Its chemical formula is H₂O.

• The freezing point of water is 0˚C.

• The boiling point of water is 100˚C.

The Hydrologic Cycle of Water

The continuous circulation of water in the Earth atmosphere is known as the Hydrologic cycle of water. There are many processes involved in the Hydrologic cycle; the important processes that the students will learn today are evaporation, transpiration, condensation, precipitation and runoff. Now let us look at all these processes in detail. 

• Evaporation: This process involves a change of state of a substance from water to gas. The evaporation process needs the energy to take place. The source of energy could be Earth, the atmosphere, the sun, humans or any objects on the surface of Earth. For example, a human body sweats after exercise or even due to a temperature change, secreting water on the skin. The basic purpose of this process is to cause the body to use its heat to evaporate the liquid by removing the heat and cooling down the body. 

• Transpiration: This process involves the evaporation of water from plants through stomata. Stomata are connected to the vascular plant tissue and are small openings that are found on the underside of the leaves. The transpiration process is caused by the humidity in the atmosphere and the moisture present in the soil. Only 1% of the transpired water is used by the plants and the rest 90% is passed into the atmosphere. 

• Condensation: This process involves a change of water vapour present in the earth atmosphere to change to a liquid state. Clouds or dews are examples of atmosphere condensation. For example, the droplets of water that we see on cold drink bottles. The change of temperature results in the water vapour changing into liquid. Condensation does not take place because of the change of the temperature but the difference in temperature is considered that is the air and dew point temperature (Dew can be formed). Cooling causes the vapour to condense. We must have observed fog, the foggy condition is the result of the air and dew point temperature being the same. Condensation and Evaporation are two opposite processes.

• Precipitation: This process involves the particles formed by the condensation process to grow large. This could result through coalescence or collision, by the rising air and thus falls to the earth. Precipitation can be in the form of rain, snow, etc. This process is the source of freshwater that we receive on Earth. 

• Runoff: This process involves the process when the water cannot be absorbed anymore due to an excess amount of precipitation. Lakes, ponds and rivers are a few examples of runoff. Evaporation of this runoff sets the cycle all over again. 

What are the Uses of Water?

There are many different uses of water, and this life-giving resource comes in handy to accomplish everything from our daily chores to helping entire industries function. 

Domestic Uses of Water

Water is important for cooking and helps in boiling, steaming and simmering food. Water has unique properties to form solutions and emulsions which make it an effective agent to help in washing clothes, dishes, and food items. Washing with water helps in removing impurities. It is required for taking showers, brushing teeth and maintaining personal hygiene. It is used for gardening at home. Water is used in several home appliances like air coolers. Water is used to generate electricity which is consumed for domestic purposes. 

We lose the water in our bodies during breathing, sweating, and digestion. The water content of the body should be replenished by drinking regularly to avoid dehydration and other health problems. Around 1 to 7 litres of water is recommended per day to avoid dehydration

Uses of Water in Agriculture

A large percentage of water is used in agriculture annually. Agriculture requires large quantities of water to grow fresh produce and sustain livestock. It is used for irrigation, pesticide and fertiliser application, frost control and crop cooling. Proper usage of water is important to manage crop yield and productivity. Farmers should follow several water conservation strategies for sustainable agriculture. 

Plants use water and sunlight for photosynthesis and produce oxygen. Agricultural water comes from surface water (rivers, streams, open canals, ponds, reservoirs and lakes), groundwater from wells and rainwater. Water is used in all traditional agriculture methods including the cultivation of rice, wheat, sugarcane, etc. 

Water quality can be affected by rampant in
dustrialization and the illegal disposal of chemicals in water and the atmosphere. Poor water quality affects the quality of the food crop and may also cause several diseases. Water contamination is the main reason for food contamination and illnesses related to the contamination. Groundwater is a safe source of quality water.                                              

Water is used for livestock, dairies, and fish farms. 

Industrial Uses of Water 

Water is used in hotels, motels, restaurants, offices, and other commercial facilities. 

It is essential in the manufacturing and production of paper, chemicals, automobiles, steel, food, textile production, dying, etc. Power plants need a significant amount of water for cooling. 

Water is a universal solvent and hence is used to dissolve several compounds in industrial production. It is widely used as a solvent and less commonly used as a catalyst. Water vapour is also used in several industrial processes. Water is used by smelting facilities and petroleum refineries. 

Industrial uses of water are processing, diluting or fabricating a product. Rivers, canals, oceans, and seas provide simple means of transportation. There will be less friction in the water compared to land transport without any obstacles. It offers economic opportunities with an effective way to transport cargo. 

Water is a source of hydroelectricity. Dams are constructed across rivers and lakes to store water which is converted to electricity using turbines. Hydroelectricity is a renewable energy source that is used across the globe. It has reduced the dependence on fossil fuels for energy. 

Water is used in the extraction of minerals, oil, and gases. It is essential for several critical mining functions. Along with being a solvent, water is used in a steam turbine and heat exchanger. 

Medicinal Uses of Water

Water has several medical uses especially in hemodialysis and dental procedures. It is used to wash surgical tools and equipment. It is also essential for hydrotherapy. 

Contamination of water with pathogens is an important concern in the healthcare setting as the immune system is weakened in some patients. The waterborne disease can spread through direct contact, ingestion, in-direct contact, and inhalation, aspiration of water and blood contact. Water should be thoroughly treated before it is used in hospitals and clinics. Clinicians should take appropriate measures to avoid contaminating water that will be ingested by the patient. 

Top 5 Causes of Outbreaks Related to Water Contamination are:

•  Legionella

•  Giardia

•  Campylobacter

•  E. coli

•  Cryptosporidium, Hepatitis A, Mycobacterium, Norovirus, Pseudomonas, Salmonella 

Thus, pure water should be available for drinking to avoid such epidemics.

Vincent du Vigneaud synthesized the vasopressin for the first time. It is also known as ADH(Antidiuretic hormone), Arginine Vasopressin(AVP), or argipressin. Vasopressin is a hormone that is produced by the neurons present in the hypothalamus location, it is first synthesized as peptide prohormone, and then it is converted into AVP. The converted AVP is then transported to the axon region of the neurons. From the axon, it is terminated in the posterior pituitary, and in response to the circulation of extracellular fluid hypertonicity. It induces the differentiation of the stem cells to form cardiomyocytes, this promotes the homeostasis of the heart muscle. It is said that the life span of vasopressin is half-life as it can live in between 16 to 35 minutes. 

The decrease in the arteriole volume of blood stimulates the secretion of the vasopressin. The ADH that is measured in the peripheral blood is derived from the secretion of vasopressin from the region of the posterior pituitary gland. Cortisol can inhibit the release of ADH. Let us see how it functions, what are its uses, side effects, and much more about this substance.

Arginine Vasopressin

Vasopressin can regulate the tonicity of the fluids situated in the body. These are released in the posterior pituitary region in response to the hypertonicity, this makes the kidneys reabsorb the solute-free water and then the tonicity is returned from the nephron via tubules to circulation. Now the tonicity of the body fluids is back to normal. A consequence of this reabsorption is concentrated urine and the reduced volume of urine. It has several neurological effects on the brain. A substance that is similar to vasopressin is lysine vasopressin(LVP); it is also known as lypressin which is found in pigs that perform the same function. The synthetic version of LVP is used in humans in case of deficiency. 

The ADH Action in Kidneys and CNS are:

There are three main effects:

1. It increases the permeability of water in PCT and CCT that is distal and cortical collecting tubes, also in the inner and outer medullary collecting ducts in the kidney. This helps in the reabsorption of water and the concentrated urine is excreted. This occurs due to the insertion of water channels in the apical membrane that is found in the collecting tubules and in the collecting duct epithelial cells, due to increased transcription. The aquaporins or the water channels allow the movement of water out of the nephron down the osmotic gradient. Thus the water is reabsorbed from the filtrate back to the bloodstream. This effect is done with the help of V2 receptors. ADH Vasopressin has the capability to increase the amount of calcium in the cells of the collecting duct. It can also increase the transcription of the aquaporin-2 gene through the action of cAMP, this in return increases the amount of aquaporin-2 gene molecules in the collecting duct.

2. By regulating the cell surface expression of the urea transporters, it increases the inner medullary portion of the collecting duct permeability to urea. It facilitates reabsorption in the medullary interstitium. It travels through the concentration gradient that is created for removing the water from certain ducts such as connecting tubules, outer medullary collecting duct, and cortical collecting duct. 

3. Across the ascending loop of the Henle, the acute increase in sodium absorption takes place. This can add the countercurrent multiplication which helps in the proper reabsorption of water in the collecting duct and the distal tubule. 

• Central Nervous System: 

The vasopressin that is released within the brain has many functions, a few of which are:

1. The neurons of the suprachiasmatic nucleus release the vasopressin in a circadian rhythm in the brain.

2. Nausea is associated with the release of the vasopressin in the posterior pituitary region. 

3. According to recent studies, it is suggested that vasopressin has analgesic effects. These effects are dependent on the sex of an individual and stress. 

Vasopressin Mechanism of Action

The ADH mechanism of action has two sites of action, one is kidneys and the other is blood vessels. 

Primarily AVP has Two Functions: 

1. During the process of circulation, in the kidney tubules of the nephron, the solute-free water is reabsorbed, where the AVP helps to increase the amount of reabsorption of the water.

2. The AVP can constrict the arterioles this can increase the peripheral vascular resistance and raises the blood pressure of the arterioles.

3. There is a possibility of another function, this AVP can directly be released from the hypothalamus to the brain. This can affect social behaviour, maternal responses to stress, and pair bonding.

Vasopressin Use

• Vasopressin is used in the treatment of diabetes insipidus, which is caused due to the absence of naturally occurring pituitary hormone in the body. 

• In the conditions that occur after surgery or during the abdominal x-rays, vasopressin is used in the treatment of these situations.

• In adults who are in shock in such persons, vasopressin is used to raise the levels of blood pressure in an emergency setting. 

Vasopressin Side Effects

If a person is allergic to chlorobutanol or vasopressin, then he should not be treated with this drug. One has to mention to the caretaker or doctor that previously they had any coronary artery disease or heart problems, kidney disease, migraine headaches, asthma, or epilepsy. If the vasopressin is given to pregnant women in their second or third trimester then it can cause premature labour contractions. A breastfeeding woman has to avoid feeding the baby if she has taken the vasopressin for about two hours. It can also cause temporary side effects such as nausea, blanching of the skin, or stomach pain.

Common Side Effects Include:

• Tingling or feeling of numbness in the feet or hands.

• Loss of colour around the mouth or lips.

• Unusual changes found in the skin especially in the lower legs or feet.

• Trouble in breathing, chest pain, or tightness in the chest region.

• Weak pulse or slow heart rate.

• No urination.

• Low sodium level.

In order to avoid these side effects, the proper dosage has to be given, it is injected into the muscle or infused into the vein. To treat the diabetes insipidus, sometimes the doctor suggests taking the vasopressin in the form of a medicine dropper or nasal spray. 

Conclusion

Vasopressin is used to manage the deficiency of the antidiuretic hormone. It is the important regulator of the excretion of renal water. Vasopressin is a hormone that is produced by the neurons present in the hypothalamus location, it is first synthesized as peptide prohormone, and then it is converted into AVP. Vasopressin can regulate the tonicity of the fluids situated in the body. The ADH action has two sites of action, one is kidneys and the other is blood vessels.

A substance produces an electrically conducting solution when it is dissolved in polar solvents such as water. These types of substances are called electrolytes. The dissolved substance can be separated in the form of cations and anions that are dispersed in the solvent uniformly. This solution is in the neutral condition, electrically. 

 

When we apply electric potential to such types of solutions, the cations present in the solution get attracted to or drawn towards the electrode that has an abundance of electrons, and in the case of anions, these are directed or attracted towards the electrode that lacks or is deficient in electrons. This opposite movement of the cations and anions results in the production of electric current. Some examples of electrolytes are soluble salts, bases, and acids. In some conditions, gases such as HCl or hydrogen chloride can also act as electrolytes; such conditions include low pressure or high temperature. 

 

Types of Electrolytes

Polyelectrolytes are formed with the help of the dissolution of some of the synthetic polymers and biological polymers that contain charged functional groups. A substance has the capability to conduct electricity when it is dissociated into ions in the solution. The classification of strong and weak electrolytes is given below. 

 

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There are two types of electrolytes:

1. Strong Electrolytes: If an electrolyte is completely dissociated into the solution, then such types of electrolytes are known as Strong electrolytes.

2. Weak Electrolytes: If an electrolyte is not completely dissociated into the solution, then such types of electrolytes are known as weak electrolytes.

 

In the case of weak electrolytes, only a small fraction of the ions are present in a dissolved solute. Let us learn more about them.

 

What Are Strong Electrolytes and Weak Electrolytes?

The solid crystalline salts start dissociating into the paired charged particles when dissolved in a solvent. This was observed by a scientist named Svante Arrhenius in the year 1884. For this invention, he received the Nobel Prize in the year 1903. The salts that dissociate in the solvent as charged particles were named by Micheal Faraday as “ions”. According to Faraday, ions are produced by the process of electrolysis. But Arrhenius found that even in the absence of an electric current, salts contain ions and hence chemical reactions occur as a result of reactions in between the ions.

 

Weak electrolytes do not completely dissociate into the solvent, whereas strong electrolytes can dissolve in the aqueous solution. The solution contains both molecules and the ions that are present in the electrolyte. Weak electrolytes ionise partially in water but strong electrolytes ionise completely. Weak bases and weak acids are considered weak electrolytes. Strong bases, strong acids, and salts are considered strong electrolytes. Salt is considered a strong electrolyte even though it has low solubility in the water because whatever the amount it dissolves in the water is completely ionised. 

Weak electrolyte examples: Acetic acid (CH₃COOH): Acetic acid is the acid that is found in vinegar. It is an electrolyte that is extremely soluble in the water. But when it is dissolved in the water, most of its original molecule remains as it is, instead of being in the ion form. This original form is known as ethanoate. The acetic acid is dissolved in the water and ionises as ethanoate and the hydronium ion. Thus, this makes acetic acid a weak electrolyte.

 

 CH₃COOH + H₂O ⇔ CH₃COO –+ H₃O +

 

Carbonic acid (CH₂O₃), Ammonia (NH₃), and Phosphoric acid (H₃PO₄) act as weak electrolytes.

 

Strong electrolytes examples: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄), sodium hydroxide (NaOH), and potassium hydroxide (KOH).

 

Difference Between Strong Electrolyte and Weak Electrolyte

 

Importance

The physiological importance and rehydration of weak electrolytes are as follows:

1. Physiological Importance: 

• The primary ions that are present in the electrolyte are sodium (Na⁺), chloride (Cl^–), magnesium(Mg ²⁺), hydrogen carbonate (HCO₃^– ), hydrogen phosphate (HPO₄^2- ), calcium(Ca²⁺), and potassium (K⁺). These electric charge
  symbols represent that the substance is of ionic nature and has an imbalanced distribution of electrons. Sodium and potassium are required to maintain fluid balance and blood pressure control.

• The complex and subtle electrolyte balance between the intracellular and extracellular environment is required for all multicellular organisms. That is in particular maintaining the precise osmotic gradient of the electrolyte is important. These types of gradients regulate the hydration of the body and maintain the pH of the blood, nerve and muscle functions. 

• The electrolyte activity between the intracellular fluid and extracellular fluid or interstitial fluid is required to maintain the activity of the muscles and neurons. The specialised protein structures that are present in the plasma membrane of the cell are known as ion channels. Through these channels, the electrolytes enter and leave the cell.

 

2. Rehydration: 

The electrolyte drinks that contain potassium and sodium salts are used in oral rehydration therapy. These salts help to replenish the concentration of electrolytes in the body that are dehydrated due to excessive consumption of alcohol, exercise, vomiting, starvation, or heavy sweating. Athletes who are found exercising in extreme conditions for more than two hours continuously have the risk of dehydration. Thus the oral consumption of electrolytes is required. The electrolyte drink can be prepared at home by using sugar, salt, and water in definite proportions. 

 

Conclusion

Electrolytes are found commonly in fruit juices, milk, nuts, vegetables and many fruits. It is found in two forms: strong and weak electrolytes. These can be strong bases and acids or weak bases and acids. Electrolytes can be measured by performing diagnostic procedures, where blood is tested with the ion-selective electrodes. The most often measured electrolytes are potassium and sodium.

Hydroxylation of Alkenes

Converting an alkene to a glycol requires adding a hydroxy group to each end of the double bond. This addition is called dihydroxylation (or hydroxylation) of the double bond. Hydroxylation of Alkenes is the oxidation of an organic compound. When oxygen is added to the C-H group and forms a bond, there is a generation of -OH groups creating COH. As oxygen reacts very slowly, there is a need for catalysts or enzymes that are also termed as Hydroxylases. Let’s take a look at a hydroxylation of alkenes example.

Different Methods of Hydroxylation

The main methods of effecting cis-hydroxylation are by reaction with potassium permanganate, with osmium tetroxide alone or as a catalyst, or with silver iodoacetate according to Woodward procedure. The most basic method of trans-hydroxylation is undoubtedly the reaction with peracids. However, the Prevost reaction and oxidation with hydrogen peroxide in alkaline solution or the presence of specific oxide catalysts are also useful procedures. The different ways of hydroxylation of alkenes are as follows.

• Hydroxylation using potassium permanganate.

• Hydroxylation using osmium tetroxide.

• Non-catalytic cis- Hydroxylation of Olefins using ester complexes.

• Catalytic Cis-Hydroxylation of Olefins with Hydrogen Peroxide.

• Catalytic Cis-Hydroxylation of Olefins with Metal Chlorates.

• Catalytic Cis-Hydroxylation of Olefins with Sodium Hypochlorite.

• Catalytic Cis-Hydroxylation of Olefins with tert-Butyl Hydroperoxide.

• Catalytic Cis-Hydroxylation of Olefins with N-methyl morpholine N-oxide.

• Catalytic Cis-Hydroxylation of Olefins with Oxygen or Air.

• Hydroxylation using Organic peroxy acids

• Hydroxylation using hydrogen Peroxide

• Hydroxylation using halogens and silver carboxylates

Woodward Reaction

Now that you understand the concept of Hydroxylation of Alkenes, we will look at Woodward reaction. Robert Burns Woodward, an American organic chemist, invented the Woodward reaction. It is a known fact that every Alkaline compound has one or more Hydroxy group present in it. Now, when these compounds are in contact with silver acetate and Iodine, they release ‘syn-diols’ or ‘cys-diols’. The ‘Syn-diols/cys-diols’ are twin -OH group that is, two Hydroxy groups adjacent with the carbons. As there is a displacement of the nucleophile, this would result in the desired form of diols. This is just opposite to a Prevost reaction as it means to remove the ‘anti-diols’ in the presence of Iodine and any benzoate and absence of water. Hence, we can conclude that Woodward reaction is just a modification of Prevost reaction that deals with the addition of ‘syn’ instead of removal. Let us try to understand it elaborately with the help of an example, as shown below. 

The image shows the cis-hydroxylation Woodward reaction, wherein an alkene reacts with silver nitrate and Iodine to form cis-diols. It is similar to the Prevost reaction.

Woodward Reaction Mechanism

In the Woodward reaction first addition of Iodine happens with alkenes, then in the presence of water, a nucleophilic displacement with acetate occurs. Thus, we get syn-diols. When the intermediate ester gets hydrolysed, we get the desired diol.

Intermediate Steps of the Mechanism are Listed Below:

1. First, Iodine and alkene react with each other and form a cyclic intermediate.

2. Again, the iodonium cyclic intermediate and acetate ion start a reaction in SN2 fashion and form a ring compound of five members.

3. Hydrolysis reaction opens the five-membered rings.

4. Next, protonation of the compound takes place followed by a hydrolysis reaction. As a result, we get diols.

Solved Problems

Question 1) The Steroid (I) Reacts with OsO4/H2O2 to Give (II) as the Major Product of 80%. Explain?

Answer 1) The dihydroxylation may be stereospecific with respect not only to the double bond but also to other stereocenters in the substance. In the case of steroid (I) the α-face of the molecule is less sterically hindered to result in vicinal diol formation on the α-side of the molecule.

Question 2) What Happens When the Following Compounds React with OsO4/H2S.

a) (Z)-3-hexene.

b) (E)-3-hexene.

Answer 2) The chemical reactions for the following compounds are as follows.

a) When (Z)-3-hexene reacts with OsO4/H2S, Meso-3,4-hexanediol is formed due to the hydroxylation of alkenes. There are two stereocenters in this reaction.

b) When (E)-3-hexene reacts with OsO4/H2S, A racemic mixture of 3,4-hexanediol is formed. There are two stereocenters in both products.

Applications of Woodward Reaction

• The Woodward reaction is used in organic chemistry and steroid chemistry.

• It is used to synthesize various forms of alkenes.

• It is used to produce long-chain olefinic compounds.

Zinc Chloride is a chemical compound, composed of zinc and chlorine. It is a colourless liquid and it exhibits hygroscopic qualities, i.e., it attracts and captures the water molecule present in the environment. It is mildly corrosive towards metals. It is an ionic salt that is essential for the synthesis of protein, fats, and cholesterol. It may cause burns to the eyes, skin, and mucous membranes.

 

There are nine different crystalline forms of zinc chloride which are currently known. These hydrates of Zinc chloride are highly soluble in water.

 

Zinc Chloride Structure

A molecule of zinc chloride has an ionic bond between the zinc cation (Zn2+) and the chloride anions (Cl–). 

 

Zinc chloride which is a colourless liquid is responsible for causing burns to the mucous membrane, eyes or skin, and also corrosive to metals. The molecular formula for zinc chloride is ZNCL2 or CL2ZN. 

Zinc chloride is also known as  zinc dichloride, butter of zinc, zinc(II)chloride. The molecular weight of the zinc is 136.3. 

Zinc chloride is mildly corrosive to metals and causes burns to the eyes, mucous membrane and skin. 

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Zinc chloride is a compound that can be prepared by a direct reaction, or by evaporating the aqueous solution formed in various reactions. Zinc chloride has nine different crystalline forms that are currently known. These hydrates of zinc chloride are mainly colourless or white in colour and all of them have a high solubility rate in water. Zinc chloride attracts the water molecules in its environment and therefore it can be said that it has hygroscopic qualities.

Physical Properties of Zinc Chloride

• Zinc Chloride formula: ZnCl2.

• Molecular Weight of Zinc Chloride: 136.315 gms/ mole

• The boiling point of Zinc Chloride is – 732 °C

• The Melting point of Zinc Chloride is – 290 °C

• Its density is 2.907.

• It forms white, odourless, very deliquescent granules. 

• Molten zinc chloride is viscous in nature and has a relatively low electrical conductivity.

 

Chemical Properties of Zinc Chloride

• When ZnCl2 is dissolved in water, the solution becomes acidic. The pH of this aqueous solution of zinc chloride having a concentration equals 6M is approx 1.

• After heating, the hydrated form of zinc chloride loses water and small quantities of ZnCl(OH) are obtained. 

• Zinc Chloride is soluble in water, glycerol, ether, and alcohol.

• Zinc chloride is deliquescent in nature, so it should be protected from sources of moisture (water vapour).

 

Preparation of Zinc Chloride

The reaction between Zinc and hydrogen chloride gives an anhydrous form of zinc chloride. The chemical equation is given below:

Zn + 2HCl → ZnCl2 + H2

Hydrochloric acid reacts with zinc sulphide to form zinc chloride and hydrogen sulphide. The chemical equation  is given by:

ZnS + 2HCl → ZnCl2 + H2S

There are some impurities present in zinc chloride samples due to the process of hydrolysis. The purification of chloride is simple due to its oxidation state Zn as +2. Purification can be done by recrystallization from hot dioxane. The purification of anhydrous zinc chloride can be done through sublimation with HCl gas, followed by the subsequent heating of the sublimate to around 400 °C with dry nitrogen gas. It can also be purified by treating it with thionyl chloride.

 

Uses of Zinc Chloride

• Zinc Chloride finds its application in different industries including pharmaceuticals, health care, paper manufacturing industry. Chemical products are also made from zinc chloride.

• Organic Product Synthesis – Organic products are synthesized in the laboratory for the preparation of Lewis acid reaction and various other organic reactions. It can be used as a catalyst in organic processes.

• Metallurgical Industry – It is used as a flux in the soldering process and cleaning agent. It is also used in the manufacturing of magnesia cement.

• Chemical Industry – Zinc chloride finds its application in the manufacture of various dyes, intermediate chemicals, and solvents like ethyl acetate. It is found in antiseptic mouthwash products.

• Printing and Textile Industry – About 64% of zinc chloride in water can be used to dissolve silk, cellulose, and starch.

• Petroleum – Zinc chloride is used as an emulsion breaker, which can separate oil from water.

• Zinc chloride is used in dry cells as an electrolyte.

• Other Uses – It is used as a condensing agent, disinfecting purposes, dehydrating agent, wood preservative, deodorant, and disinfectant.

• A mixture of zinc oxide and hexachloroethane can be used in smoke grenades. While igniting, these compo
  unds react with each other to form a smoke of zinc chloride, which serves as a smokescreen.

• The Lucas reagent used is a solution of anhydrous zinc chloride and concentrated hydrochloric acid. This reagent is useful in preparing alkyl chlorides.

• Zinc chloride is used as an alternative medicine for the cause of dead tissue,  to cure skin cancers.

 

Zinc and Its Doses 

• Infants and Children: When taken by mouth properly in the prescribed quantities, zinc is likely Healthy. When used in high concentrations, zinc is Dangerous.

• Pregnancy and Breast-Feeding: Zinc is likely safe when used in the prescribed daily quantities for most pregnant and breast-feeding women (RDA). Zinc, however, is potentially unsafe when used by breast-feeding women at high doses and likely unsafe when used by pregnant women at high doses. Not more than 40 mg of zinc should be taken per day by pregnant women over the age of 18, no more than 34 mg per day should be taken by pregnant women aged 14 to 18 years. No more than 40 mg of zinc per day should be taken by breastfeeding women over the age of 18, no more than 34 mg per day should be taken by breastfeeding women aged 14 to 18.

• Alcoholism: Excessive, long-term consumption of alcohol is related to low absorption of zinc in the body. 

• Kidney Disease: The risk of having kidney disease rises with low zinc in the diet. People with hemodialysis kidney disease are also at risk for zinc deficiency and may need zinc supplements. 

• Vegetarianism: Vegetarian diets are often associated with lower absorption of zinc. This form of diet is also seen as a risk factor for the depletion of zinc. But in the long term, the body adapts. Zinc absorption and zinc loss elimination are getting stronger.

Conclusion:

You can learn more about the affair between Zinc and Chlorine through this wonderfully crafted article. You can use them from an exam point of you or to enrich your knowledge.