Chemistry Concepts Explained: Reactions, Polymers, and More

Posted on Mar 7, 2025 in Chemistry

Rosenmund Reaction

In the presence of BaSO₄, an aldehyde is obtained upon reduction of an acid chloride. This reaction is called the Rosenmund reaction. The product is an aldehyde, and the reagent is Pd/BaSO₄.

Polypeptide Bond Formation

A peptide bond is formed from amino acids between one -COOH group and another -NH₂ group by the removal of one molecule of water.

Increasing Order of Electron Affinity for Halogens

I₂ < Br₂ < F₂ < Cl₂

Usefulness of DNA Fingerprinting

Individual organisms are identified using patterns of DNA pieces caused by specific enzymes in DNA fingerprinting of humans, other animals, plants, or any other organism with DNA. DNA fingerprinting is useful in paternity analysis, criminal cases, and many studies of ecology and development.

Synthetic Polymers: Definition and Examples

Polymers synthesized in the laboratory by humans are called synthetic polymers. Examples of synthetic polymers include polythene and nylon. PVC is also a synthetic polymer. An example of a condensation polymer is polyester.

Iron Ores: Names and Formulas

The two major ores of iron are hematite and magnetite. The chemical formula of hematite is Fe₂O₃, and the chemical formula of magnetite is Fe₃O₄.

Cryolite in Aluminum Extraction

Aluminum metal is obtained from the electrical decomposition of alumina. Alumina has a very high melting point, and its electrical conductivity is low. The mixing of cryolite reduces the melting point of alumina and increases its electrical conductivity.

Schottky Defect

This defect is a vacancy defect in ionic solids that occurs due to the missing of both cations and anions. It decreases the density of the substance. Examples include NaCl, KCl, CsCl, and AgBr.

Mole Fraction Definition

In a solution, the ratio of the number of moles of a component to the total number of moles present in the solution is called the mole fraction of the component.

Raoult’s Law and Relative Vapor Pressure

For a solution of volatile liquids at a given temperature, the partial vapor pressure of each component in the solution is equal to the vapor pressure of the pure component multiplied by its mole fraction.

Physical Adsorption vs. Chemical Adsorption

Physical Adsorption: Van der Waals bonds, reversible, 22-40 kJ/mol.

Chemical Adsorption: Ionic and covalent bonds, irreversible, approximately 80 kJ/mol.

Brownian Movement

When colloidal particles move in a zigzag manner, Brownian movement occurs.

Carbylamine Reaction

When ethylamine or any other primary amine is heated with chloroform and an alcoholic KOH solution, ethyl isocyanide is formed, which has a very bad smell.

C₂H₅NH₂ + CHCl₃ + KOH → C₂H₅NC + 3KCl + 3H₂O

Why Transition Elements Form Complex Compounds

Transition metals usually form more complex or coordinated compounds as they contain vacant orbitals, which can accept an electron pair from a Lewis base. This means that the ligand must have at least one pair of non-bonding electrons that can be donated to the metal ion.

Molal Elevation Constant

The molal elevation constant is equal to molality when one mole of solute dissolves in 1 kg of solvent. Unit: Kelvin kg mol^-1.

Abnormal Molecular Mass

The molecular mass of any electrolyte after association and dissociation is called abnormal molar mass.

Sorption Definition

The process in which both adsorption and absorption occur is called sorption. Example: In the sugar industry, animal charcoal enhances and absorbs colored substances.

Flux and Slag

Flux is a substance added along with carbon during smelting to remove impurities. Slag is a chemical substance formed after the combination of impurities from the ore and the flux, and it is lighter in weight than the molten metal. It may be basic or acidic and is a neutral compound in nature.

Atomic Radius of Noble Gases

Atomic radii of noble gases are comparatively large as they only have a van der Waals radius, which is expected to be large, while other members of the periodic table have either covalent or metallic radii because noble gases have no attraction or repulsion.

Point Defect

A deviation from the ideal arrangement around a point in a crystalline substance is called a point defect.

Reaction of Benzene with Methyl Bromide

Toluene is formed when benzene reacts with methyl chloride in the presence of anhydrous AlCl₃. This reaction is called the Friedel-Crafts reaction.

Power Alcohol

Power alcohol is a liquid mixture that contains petrol, ethanol, and a small amount of benzene. Power alcohol is used to generate energy for various functions in the field of automobiles. It is also used as a vehicle fuel and is cheaper than petroleum, containing 80% petrol and 20% ethanol.

Major Oxidation States of Lanthanoid Elements

The most common oxidation state of all lanthanoid elements is +3. Earlier, some metals were considered to have a +2 oxidation state. Some lanthanoid metals display a +4 oxidation state on rare occasions.

Examples of Polymers

Synthetic rubber: Neoprene
Structure polymer: Nylon 6,6
Additional polymer: Buna-S

Preservatives

Chemical substances used to protect food from bacteria for a long time are called preservatives. Examples include sodium benzoate, sodium metabisulfite, vinegar, tartaric acid, citric acid, and ethyl alcohol.

Denaturation of Protein

Biological activity is destroyed when a protein is heated or mixed with a concentrated acid or alkali solution. The bonds between protein molecules break, and their structure and pH value change. This is called denaturation of protein.

Solution of Gas in a Solid

Hydrogen in palladium is a solid solution where hydrogen gas is the solute and palladium is the solid solvent.

Isotonic Solution

An isotonic solution is when two solutions have equal concentrations of solutes across a semi-permeable membrane.

Utility of Alumina in Aluminum Extraction

In the extraction of aluminum, the importance of the component is to concentrate pure alumina from bauxite.

Soap Action

When soap is used on smooth, lubricated clothes with oil, soap molecules form a micelle around the oil drops or lubricant. The anti-water, anti-hydrocarbon part of the micelle attracts the lubrication, and the water-attracting polar part remains outward. In this way, the lubrication surrounds the micelle.

Metal Purification by Bessemerization

Bessemerization is a method of metal purification in which the impure metal obtained is drained into a furnace, and a stream of air is flowed through it. This causes the impurities to be transformed into oxides and removed with silica, resulting in a purified metal. It is used in the purification of copper and is performed in a Bessemer converter.

IUPAC Names

Lactic acid: 2-hydroxypropanoic acid
Tartaric acid: 2,3-dihydroxybutanedioic acid

Aniline vs. Ethylamine Basicity

The nitrogen atom in ethylamine has a tendency to donate electrons due to sp³ hybridization, so ethylamine easily behaves like a Lewis base. Aniline is a weaker base than ethylamine.

Bleaching Property of Ozone

Ozone works as an oxidizing agent. This effect causes the bleaching process of ozone to incorporate oxygen into the particles of colored substances, causing the color to appear or disappear.

Strong vs. Weak Electrolytes

Strong Electrolytes: Substances that become completely ionized in an aqueous solution. Examples include NaCl, NH₄Cl, KNO₃, HCl, and HBr.

Weak Electrolytes: Substances that ionize to a certain extent. Examples include CH₃COOH and HCN.

Alcohol Boiling Point vs. Alkane

The boiling point of alcohol is higher than its corresponding alkane because alcohol contains intermolecular hydrogen bonds due to the high electronegativity of oxygen. Therefore, alcohol requires a large amount of energy to break these hydrogen bonds.

Cannizzaro Reaction

Aldehydes that have no alpha hydrogen undergo the Cannizzaro reaction. It is a disproportionation reaction in which one molecule gets oxidized, and the second gets reduced.

2HCHO + NaOH → CH₃OH + HCOONa

Artificial Sweeteners

Substances that provide sweetness in food without increasing the calories of the body are called artificial sweeteners. They are inactive and harmless and are excreted unchanged from the body in urine. Examples include saccharin and aspartame.

Conversion of Ethyl Alcohol to Chloroform

A mixture of bleaching powder (Ca(OCl)₂) is used in the process of preparing chloroform in the laboratory by heating with ethanol or acetone. Here, the bleaching powder acts as an oxidizing, chlorinating, and hydrolyzing agent.

Velocity Constant of a Chemical Reaction

The rate constant is a constant measuring the speed of a chemical reaction. It indicates the rate at which reactants are converted into products. It is represented by (k) and depends on the temperature of the reaction and the concentration of the reactants.

Hell-Volhard-Zelinsky (HVZ) Reaction

In the presence of Cl₂ or Br₂ and red phosphorus, alpha-halo carboxylic acids are formed from hydrocarboxylic acids. Halogenation continues until all alpha hydrogen atoms are replaced by halogen.

Elimination Reaction

When an alkyl halide is treated with alcoholic KOH, an elimination reaction takes place. For example, alcohol forms alkyl halide.

CH₂-CH₂-Cl + KOH → CH₂=CH₂ + KCl + H₂O

Fehling’s Reaction

Fehling’s reagent is a reagent that contains sodium potassium tartrate in an alkaline solution of copper sulfate. It is dark blue and is used to distinguish between ketones and aldehyde functional groups.

Pseudo-First-Order Reaction

Pseudo-first-order reactions are reactions that are not of the first order, but the concentration of one or more reactants appears to be of the first order compared to other reactants. Here, pseudo means fake. This reaction is binary, but its order is one.

First-Order Reaction

A reaction in which the reaction rate is determined by the variation of one concentration term only is said to be a first-order reaction. Let us consider a simple first-order reaction in which the reactant A gives a product. Let the initial concentration of the reactant A be (a) mol/liter. Suppose that x moles/liter of A decompose in time t, leaving behind (a – x) mol/liter.

For a first-order reaction, the rate of reaction is directly proportional to the initial concentration of the reactant. Thus, the rate of the above reaction at time t is given by:

dx/dt ∝ (a – x)

dx/dt = k(a – x), where k is the rate constant of the reaction.

dx/(a – x) = kdt (i)

To get the value of k, we integrate the above equation:

Integrating (i), we get -log(a – x) = Kt + I, where I is the integration constant.

When t = 0 and x = 0, therefore, from equation (ii), we get -log(a) = I.

Substituting the value of I in equation (ii), we get:

-log(a – x) = Kt – log(a)

Kt = log(a) – log(a – x)

Kt = log(a/(a – x))

K = (1/t) * log(a/(a – x))

Henry’s Law

Henry’s law, also known as the effect of pressure on the solubility of gases in liquids at a particular temperature, states that the mass of a gas dissolved in a given volume of liquid at a constant temperature is directly proportional to the pressure of the gas present in equilibrium with the liquid. Mathematically, m = KP, where m is the mass of the gas dissolved in a unit volume of the solvent.

Important Applications of Henry’s Law:

To increase the solubility of CO₂ in soft drinks and soda water, the bottle is sealed under high pressure.
Deep-sea divers use oxygen diluted with less soluble helium as a breathing gas to minimize the painful effects accompanying decompression.
In the lungs, where oxygen is present in air with high partial pressure, hemoglobin combines with oxygen to form oxyhemoglobin. In tissues where the partial pressure of oxygen is low, it releases oxygen for utilization in cellular activity.

Narcotics

Narcotics are compounds that possess a general depressant action on the central nervous system. They can be classified into sedatives, hypnotics, tranquilizers, and general anesthetics.

Sedatives: Cause a milder form of depression. The most widely used sedatives are bromides and bromo compounds. KBr is the most commonly used. Bromonalaton and valido bromine are used as sedatives.
Tranquilizers: Compounds that help in reducing anxiety by acting on the nervous system. They induce sleep and can be habit-forming. Examples include luminal and equanil.
Anesthetics: Compounds used to produce unconsciousness and muscular relaxation sufficient to allow the performance of surgical operations. Examples are ethylene, divinyl ether, and chloropropane. For small operations and tooth extractions, the limited area is made senseless either by injecting or by local application of drugs called local anesthetics. Examples are cocaine, novocaine, and xylocaine.

Tests to Distinguish Compounds

Ethanol and Acetaldehyde: Acetaldehyde gives a silver mirror test with Tollen’s reagent. Ethanol does not give this test. Acetaldehyde reduces Fehling’s solution and gives a red precipitate of Cu₂O, but ethanol does not give this test.
Phenol and Carboxylic Acid: Carboxylic acids chemically react with sodium bicarbonate and give off CO₂. Phenol does not give this test.
Aldehyde and Ketone: Aldehydes give the silver mirror test with Tollen’s reagent and a precipitate of Cu₂O with ammonium copper sulfate solution.
Formic Acid and Acetic Acid: Formic acid has reducing character and reduces Tollen’s reagent to give a silver mirror, reduces Fehling’s solution to give a red precipitate of Cu₂O, and reduces mercuric alcohol chloride, but acetic acid does not give these tests.
Primary, Secondary, and Tertiary Alcohols: Test with Lucas reagent: Tertiary (3°) alcohols become immediately turbid on reaction with Lucas reagent, secondary alcohols after 5 minutes, and primary alcohols become turbid last.

Reactions

Calcium Formate Heated Strongly: Calcium formate decomposes upon heating to produce formaldehyde and calcium carbonate. (HCOO)₂Ca → HCHO + CaCO₃
Methanol Reacts with Ammonia: If it’s pure ammonia, you would get a solution of ammonia in methanol. There would effectively be no reaction since ammonia is a weak base, and methanol is much less acidic than water. CH₃OH + NH₃ –ZnCl₂–> CH₃NH₂ + H₂O

DNA vs. RNA

DNA: DNA is a double-stranded helix in which two strands are coiled spirally in opposite directions. The sugar molecule is deoxyribose. The nitrogenous base uracil is not present. DNA molecules have very high molecular weights, varying from 6 million to 16 million. DNA has the unique property of replication.

RNA: RNA is a single-stranded structure. The sugar molecule is ribose. The nitrogenous base thymine is not present. RNA molecules are much smaller, with molecular weights ranging from 20,000 to 40,000. RNA usually doesn’t replicate.

Nucleic Acids

Nucleic acids are found in all living cells in the form of nucleoproteins. They constitute an important class of biomolecules. Nucleic acids are the genetic material of the cells and are responsible for the transmission of hereditary effects from one generation to another. They also carry out the synthesis of proteins. Nucleic acids are biopolymers. The genetic information about the nucleic acids controls the structure of proteins, including enzymes, and thus the entire metabolic activity in the living organism.

Carbohydrates

Carbohydrates are naturally occurring organic compounds and are a major source of energy for our bodies. In plants, carbohydrates are formed as a result of photosynthesis. In animal systems, carbohydrates undergo decomposition to form carbon dioxide and other compounds, releasing energy needed for the body.

Composition of Carbohydrates:

The chemical formula of carbohydrates suggests that these are hydrates of carbon. For example, glucose may be represented as C₆H₁₂O₆, while sucrose is C₁₂H₂₂O₁₁. But this definition has certain limitations:

Compounds like formaldehyde (CH₂O) and acetic acid (C₂H₄O₂) are hydrates of carbon but do not show characteristics of carbohydrates.
Similarly, compounds like rhamnose and deoxyribose are carbohydrates but not hydrates.

The definition of carbohydrates has been modified, and they may be defined as polyhydroxy aldehydes or polyhydroxy ketones or substances that generally give these on hydrolysis, contain at least one chiral carbon, and are therefore optically active.

Classification of Carbohydrates:

Classification of carbohydrates is done in three ways:

On the basis of molecule size, carbohydrates have been classified into three types: a. Monosaccharides, b. Oligosaccharides, c. Polysaccharides
Based on taste, carbohydrates with a sweet taste are called sugars, while those without a sweet taste are called non-sugars. All monosaccharides and oligosaccharides are sugars, while polysaccharides are non-sugars.
Reducing and non-reducing sugars: Carbohydrates that reduce Tollen’s reagent and Fehling’s solution are called reducing sugars, while those that don’t reduce these are called non-reducing sugars. For example, glucose and fructose.

Acid Rain

Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions and a low pH value. It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxides, which react with water molecules in the atmosphere to produce acids. Chemically, acid rain can cause paint to peel, corrosion of steel structures of bridges, and erosion of stone statues.

Sources of Iodine

Due to its reactivity, iodine is not found in nature in a free state. Its main sources are seaweed, Chilean saltpeter, and natural brines.

Extraction of Iodine from Seaweed:

Seaweed (Laminaria) contains iodine. Seaweed is well-dried and burnt in deep pits carefully so that iodine doesn’t get destroyed. The obtained ash is called kelp, which contains 0.4 to 1.3% iodine. Kelp is dissolved in water, and the solution is partially crystallized to remove salts.

Glass as a Supercooled Liquid

Glass is an amorphous solid. Like liquids, it has a tendency to flow, though very slowly. This is evident from the fact that the glass panes in the windows of old buildings are invariably found to be slightly thicker at the bottom than at the top. This is because the glass flows down very slowly, making the bottom portion slightly thicker.

Salt Bridge

In electrochemistry, a salt bridge is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell, a type of electrochemical cell). Salt bridges usually come in two types: glass tubes and filter paper.

Carbonium Ion (Carbocation)

A carbonium ion (carbocation) is an ion with a positively charged carbon atom. Among the simplest examples are methanium (CH₃⁺) and ethanium (C₂H₇⁺). Some carbocations may have two or more positive charges on the same carbon atom or on different atoms, such as ethylene dication (C₂H₄²⁺). They are classified into two categories according to the valence of the charged carbon.

IMPORTANT NOTE