Current Affairs JEE Main & Advanced

General Rules For Naming Organic Compounds

In the common system, all the isomeric alkanes (having same molecular formula) have the same parent name. The names of various isomers are distinguished by prefixes. The prefix indicates the type of branching in the molecule. For example, (1) Prefix n-(normal) is used for those alkanes in which all the carbon atoms form a continuous chain with no branching. \[\underset{n-\text{Butane}}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,\]; \[\underset{n-\text{Pentane}}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,\] (2) Prefix iso is used for those alkanes in which one methyl group is attached to the next-to-end carbon atom (second last) of the continuous chain. \[\underset{\text{Isobutane}}{\mathop{\underset{\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{\,|}{\mathop{C{{H}_{3}}-CHC{{H}_{3}}}}\,}}\,}}\,\] \[\underset{\text{Isopentane}}{\mathop{\underset{C{{H}_{3}}\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-CH-C{{H}_{2}}C{{H}_{3}}}}\,}}\,}}\,\] \[\underset{\text{Isohexane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-CHC{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,}}\,}}\,\] (3) Prefix neo is used for those alkanes which have two methyl groups attached to the second last carbon atom of the continuous chain. \[\underset{\text{Neopentane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}}{\mathop{\overset{\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{|}{\overset{|}{\mathop{C{{H}_{3}}-C-C{{H}_{3}}}}}\,}}\,}}\,}}\,\] \[\underset{\text{Neohexane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\overset{\,C{{H}_{3}}\,\,\,\,\,\,\,\,}{\mathop{\underset{\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\overset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-C-C{{H}_{2}}-C{{H}_{3}}}}}\,}}\,}}\,}}\,\]

Catgeory: JEE Main & Advanced

Alkyl groups

These are univalent groups or radicals obtained by the removal of one hydrogen atom from a molecule of a paraffin. The symbol 'R' is often used to represent an alkyl group. \[\begin{align} & \text{(Alkane) }{{C}_{n}}{{H}_{2n+2}}\xrightarrow{-H}{{C}_{n}}{{H}_{2n+1}}\text{ (Alkyl group)} \\ & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(R-H)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(R-) \\ \end{align}\] Alkyl groups are named by dropping-ane from the name of corresponding paraffin and adding the ending'yl.

Parent saturated hydrocarbon	Name of the alkyl group	Structure
Methane	Methyl	\[C{{H}_{3}}-\]
Ethane	Ethyl	\[C{{H}_{3}}-C{{H}_{2}}-\]
Propane	n-Propyl	\[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\]
Butane	n-Butyl	\[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-\]

Alkyl groups derived from saturated hydrocarbons having three or more carbon atoms exist in isomeric forms.

Similarly, removal of different H atoms in pentane gives the following radicals : \[\underset{n-Pentyl}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}-}}\,\];\[\underset{\text{Isopentyl}}{\mathop{\underset{C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}CHC{{H}_{2}}C{{H}_{2}}-}}\,}}\,}}\,\]; \[\underset{\text{Neopentyl}}{\mathop{\underset{\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{|\,\,\,}{\mathop{\overset{\,\,\,\,C{{H}_{3}}}{\mathop{\overset{|\,\,\,\,}{\mathop{C{{H}_{3}}CC{{H}_{2}}-}}\,}}\,}}\,}}\,}}\,\];\[\underset{\sec -\text{Pentyl}}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}CHC{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,}}\,\]; \[\underset{tert-\text{Pentyl}}{\mathop{\overset{\text{C}{{\text{H}}_{\text{3}}}\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,}{\mathop{\overset{|\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}CC{{H}_{2}}C{{H}_{3}}}}\,}}\,}}\,}}\,\] Unsaturated groups or radicals more...

Catgeory: JEE Main & Advanced

Classification Of Carbon Atoms In Organic Compounds

The carbon atoms in an alkane molecule may be classified into four types as primary \[(1{}^\circ ),\] secondary \[(2{}^\circ ),\] tertiary \[(3{}^\circ ),\] and quaternary \[(4{}^\circ ).\] The carbon atoms in an organic compound containing functional group can be designated as a, b, g, d. \[\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{\,}^{{{1}^{o}}}}C{{H}_{3}}}{\mathop{\overset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{\,}^{{{1}^{o}}}}C{{H}_{3}}}{\mathop{\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}{\overset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}{\mathop{^{{{1}^{o}}}C{{H}_{3}}{{-}^{{{2}^{o}}}}C{{H}_{2}}{{-}^{{{4}^{o}}}}C-}}}\,}}\,}}\,\underset{^{{{1}^{o}}}C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{^{{{3}^{o}}}CH{{-}^{{{1}^{o}}}}C{{H}_{3}}}}\,}}\,\]

Catgeory: JEE Main & Advanced

Nomenclature Of Organic Compounds

Nomenclature means the assignment of names to organic compounds. There are two main systems of nomenclature of organic compounds. (1) Trivial system : This is the oldest system of naming organic compounds. The trivial name was generally based on the source, some property or some other reason. Quite frequently, the names chosen had Latin or Greek roots. For example, (i) Acetic acid derives its name from vinegar of which it is the chief constituent (Latin : acetum = vinegar). (ii) Formic acid was named as it was obtained from red ants. The Greek word for the red ants is formicus. (iii) The names oxalic acid (oxalus), malic acid (pyrus malus), citric acid (citrus) have been derived from botanical sources given in parentheses. (iv) Urea and uric acid have derived their names from urine in which both are present. (v) The liquid obtained by the destructive distillation of wood was named as wood spirit. Later on, it was named methyl alcohol (Greek : methu = spirit; hule = wood). (vi) Names like glucose (sweet), pentane (five), hexane (six), etc. were derived from Greek words describing their properties or structures. (vii) Methane was named as marsh gas because it was produced in marshes. It was also named as fire damp as it formed explosive mixture with air.

Compound

Common name

Compound

Common name

\[C{{H}_{4}}\]

Methane

\[CHC{{l}_{3}}\]

Chloroform

\[{{C}_{2}}{{H}_{2}}\]

Acetylene

\[CH{{I}_{3}}\]

Iodoform

\[{{H}_{3}}CC{{H}_{2}}C{{H}_{2}}C{{H}_{3}}\]

n-Butane

\[C{{H}_{3}}CN\]

Acetonitrile

\[{{({{H}_{3}}C)}_{2}}CHC{{H}_{3}}\]

Isobutane

\[C{{H}_{3}}COOH\]

Acetic acid

\[{{({{H}_{3}}C)}_{4}}C\]

Neopentane

\[{{C}_{6}}{{H}_{6}}\]

Benzene

\[HCHO\]

Formaldehyde

\[{{C}_{6}}{{H}_{5}}C{{H}_{3}}\]

Toluene more...

Catgeory: JEE Main & Advanced

New High Performance Materials

(1) Carbon fibres : These fibres are stronger than steel, stiffer than titanium and lighter than aluminium. Carbon fibres are produced in a number of ways, and from a variety of starting materials or precursors such as viscose rayon, polyacrylonitrile, pitch, resins, gases such as (methane, and benzene). Their characteristics are strongly influenced by the manufacturing techniques employed. Carbon fibres reinforced in a light weight matrix, generally an epoxy resin, polyester resin or polyamide, are called Carbon Fibre Reinforced Plastics (CFRP). When the carbon fibres are reinforced in a carbon matrix, they are known as Carbon Fibre Reinforced Carbon (CFRC), commonly known as carbon-carbon composites. On the basis of the characteristics of carbon fibres, carbon firbre reinforced plastics (CFRP) and carbon fibre reinforced carbons (CFRC), their applications can be broadly classified into three categories, (i) High technology sector including aerospace, military and nuclear fields. (ii) General engineering sector including sports, transportation and chemical fields. (iii) Biomedical sector. Carbon fibres in India are mainly used in defence sector as nose tips and head shields of missiles (like 'Agni') by DRDO, Hyderabad, and in the aerospace sector by ISRO and other aerospace organizations for producing components parts, nozzles of rockets/missiles. (2) Ceramics : The term ceramics comes from the Greek word keramikos which means burnt stuff, indicating thereby, that desirable properties of these materials are normally achieved through a high-temperature heat treatment process called firing. In the past, the most important materials in this class were the traditional ceramics, prepared from clay, (kaoloinite) a silicate. In the category of traditional ceramics we have porcelain, bricks, tiles, glass and temperature resistant ceramics. Most ceramic materials fall into an application-classification scheme which is given below, (i) Clay products : Porcelain, pottery, tablewares, sanitary fittings, building bricks, tiles and sewer pipes. (ii) Glass ceramics : Kitchenware. (iii) Refractory materials : Refractory bricks used as furnace linings. (iv) Abrasive ceramics : Cutting and grinding tools. (familiar examples are silicon and tungsten carbides). Recently, a family of ceramics have been found to be superconductors with high critical temperatures. One such material is yttrium, barium, copper oxide, which has a critical temperature of about 92 K. New super conduction ceramic materials reported to have even higher critical temperatures have been and are currently being developed. Several of these materials and their critical temperatures are listed below, Super conducting ceramic materials and their critical temperatures. more...

Catgeory: JEE Main & Advanced

Detergents

As a result of high dissolving power, the naturally occurring water always contains dissolved materials, particularly ionic substances. Hard water contains certain metal ions, such as \[C{{a}^{2+}}\]and \[M{{g}^{2+}}\]. These ions react with soap. (sodium salts of stearic and similar organic acids), to produce a curdy precipitate of calcium and magnesium salts. This precipitate adheres to clothing and blocks the ability of soaps to remove oil and grease from fabrics. Synthetic detergents are very similar to the salts of fatty acids found in soap, except that they are manufactured chemically from materials others than animal fats, Examples include salts called sodium alkylbenzenesulphonates, which have the general structure.

The anions of synthetic detergents donot precipitate in the presence of \[C{{a}^{+2}}/M{{g}^{+2}}\], so their cleansing action is not affected by hard water.

Types of detergents (1) Anionic detergent : Long chain alcohols are used in the manufacture of some of the synthetic anionic detergents. The long chain alcohols are treated with concentrated sulphuric acid to form alkyl hydrogen sulphates of high molecular mass and finally the alkyl sulphates are neutralized with alkali to form salts.

The single anionic detergents is largest use today in household detergents is alkylbenzene-sulphonate.

(2) Cationic detergent : These are mostly acetates or chlorides of quaternary amines. Being more expensive than the anionic detergents they find limited use. Such detergents however, possess germicidal properties and are used quite extensively as germicides. Cetyltrimethyl-ammonium chloride, is an example. \[\left[ \underset{\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}}\,}{\mathop{\overset{\overset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}}\,}{\mathop{C{{H}_{3}}{{(C{{H}_{2}})}_{15}}-N-C{{H}_{3}}}}\,}}\, \right]\ C{{l}^{-}}\] Cationic Detergent (3) Non ionic detergent : Esters of high molecular mass formed by reactions between polyethylene glycol and stearic acid.

Some liquid dishwashing detergents are of nonionic type.

Detergent molecules associated with branched hydrocarbon tail which is a source of pollution. The hydrocarbon side chain stops bacteria from attacking and breaking the chains. This results in slow degradation of detergent molecules leading to their accummulation. These days the amount of branching can be kept to a minimum. Unbranched chains are more prone to attack by bacteria so the detergents are more easily biodegraded and pollution is prevented.

Catgeory: JEE Main & Advanced

Plant Growth Hormones

These are the organic substances which are synthesized in minute quantities in one part of the plant body and are transported to another part where they influence specific physiological processes to regulate growth, differentiation and development. Plant growth hormones are grouped into two main types : (i) growth promoters (e.g., auxins, gibberellines, cytokinins etc.) and (ii) growth inhibitors (e.g. ethylene, abscisic acid, maleic hydrazide etc.) Many of these hormones, especially the synthetic ones are now-a-days widely used in agricultural practices e.g., as weedicides (2, 4-Dichlorophenoxyacetic acid or 2, 4-D), as rooting hormones (Naphthalene acetic acid or N.A.A. etc.), to induce flowering in certain plants (e.g., N.A.A., I.B.A.), to prevent pre-mature fruit drop (e.g., 2, 4-D, I.A.A., I.B.A., etc.), for storage of potato tubers–where they prevent sprouting (e.g., N.A.A.), to increase sweetness of fruits (e.g., I.B.A.), to increase yield of certain crops (e.g. gibberellins increase yield of pea, bean tomatoes, pepper, cucumber, lettuce, cabbage, etc.), in tissue culture (e.g. cytokinins), artificial ripening fruits like banana, mango (e.g. ethylene).

Catgeory: JEE Main & Advanced

Pheromones, Sex Attractants

A major drawback with chemical insecticides is their lack of specificity. Non-specificity of insecticides may kill helpful insects, such as honeybees, which aid in pollination. The more specific we make our insect control, the less we will disrupt the environment. Although, in the past, it looked as if specific control was beyond the scope of chemistry, but some developments have shown that it is entirely possible to control populations of certain insects very effectively and specifically using substances known as pheromones. Pheromones provide chemical means of establishing communication. There are sex, trail and defense pheromones to mention a few. One of the most important roles pheromones play is as sex attractants. Sex pheromones tell the honeybee which flower to pollinate. The sex pheromones are remarkably powerful. A few hundred molecules may be all that are necessary to invoke a response. In addition to this fascinating parameter, it has been claimed that the sex attractants in some species can attract males from over two miles away. (The sex attractants are usually emitted by the females, although there are some male insects which also produce them). By baiting a trap with a small amount of sex attractant of an insect pest, one can collect all the males in the vicinity. They may then be disposed of or sterilized. Since mating cannot take place, the reproductive cycle is halted and the pest is controlled. The advantages to this method are immediately obvious. It is very specific since, (except in very rare instances), each insect has its own attractant. There is no spraying, hence no pesticide residues. In addition, the concentration of the attractants is so small that there would be no effect on any other species, even indirectly. For example, the gypsy moth attractants, attracts male moths in the area when a trap is baited with only \[1\times {{10}^{-9}}g\]. Gypsy moths are highly voracious eaters and will completely denude trees if they go unchecked.

Catgeory: JEE Main & Advanced

Chemicals in food

Many chemicals are added to food for their preservation and enhancing their appeal. These include flavourings, sweeteners, dyes, antioxidants, fortifiers, emulsifiers and antifoaming agents. With the exception of the preservatives, fortifying agents, antioxidants and artificial sweeteners, the remaining classes of chemicals mentioned above are added either for ease in processing or for cosmetic purposes, in the real sense these have no nutritive value. (1) Antioxidants : Antioxidants are the important and necessary food additives. These compounds retard the action of oxygen on the food and thereby help in its preservation. These act as sacrificial materials, i.e., these are more reactive towards oxygen than are the materials they are protecting. They also reduce the rate of involvement of free radicals in the aging process. The two most familiar antioxidants used are butylated hydroxy toluene (BHT) and butylated hydroxy anisole (BHA). The addition of BHA to butter increases its storage life from months to years. The two have the following structures.

Sometimes BHT and BHA are added in combination with citric or ascorbic acids to produce a more active synergietic effect. Sulphur dioxide and sulphite are useful antioxidants for wine and beers, sugars syrups and cut peeled or dried fruits and vegetables. (2) Preservatives : The preservatives prevent spoilage of food due to microbial growth. The most common preservative used is sodium benzoate, \[{{C}_{6}}{{H}_{5}}COONa.\] It is metabolized by conversion to hippuric acid, \[{{C}_{6}}{{H}_{5}}CONHC{{H}_{2}}COOH\] which ultimately is excreted in the urine. Salts of propionic acid and sorbic acid are also used as preservatives. (3) Artificial sweetener : The artificial sweeteners are another type of food additives. The first popular artificial sweetener was saccharin. It was marketed as its water soluble sodium or calcium salt. Saccharin is approximately 300 times sweeter than cane sugar. It has proved to be a lifesaver for countless diabetics and is of great value to people who need to control intake of calories. Besides saccharin, the other commonly marketed artificial sweeteners are described here. Aspartame is unstable at cooking temperatures, limiting its use as a sugar substitute to cold foods and soft drinks. Alitame is more stable than aspartame during cooking. One potential problem with alitame and similar type of high-potency sweetners is the difficulty in controlling sweetness of food. Sucralose is predicted to become a great commercial success.

Material

Elements present in the material

Critical temp./K

Artificial Sweetner

Structural Formula

Sweetness value in comparison to more...

Catgeory: JEE Main & Advanced

Chemical in cosmetics

The word cosmetics is derived from the Greek word Kosmetikos. It means decorating. beautifying or improving complexion of skin. In India from the ancient times Henna has been used to decorate hands and some other parts of the body. Some of the cosmetics which find use in daily life are discussed below, (1) Creams : Creams are used for facial make-up. These are often classified as : cleansing creams, cold creams, vanishing creams, sunburn creams and bleach creams. (i) Cleansing creams : Remove facial make up, surface grime, lipstic and oil. (ii) Cold creams : Lubricate the skin and prevent roughness and chaffing. (iii) Vanishing creams : Keep the skin cool and oily. (iv) Sunburn creams : Save the skin from sunburn in summer. (v) Bleach cream : Exert a bleaching effect on dark skin. (2) Perfumes : Perfumes are the materials, used to provide fragrance. Several requirements have to be fulfilled to make a good perfume and any material, which just gives good smell, may not be a perfume. A perfume invariably consists of three ingredients : a vehicle, fixative and odour producing substance. (i) Vehicle : The vehicle is also called solvent. The role of the solvent is to keep the odour-producing substances in solution. Ethanol and water mixture is the most common vehicle used in perfumery. (ii) Fixative : The function of the fixative is to equalize the rate of evaporation of various odouriferous components of the perfume by suitably adjusting their volatility. Sandalwood oil finds use as fixative. Other substances used as fixative are benzoin, glyceryl diacetate and esters of cinnamyl alcohol. (iii) Odourous substances : Both natural and synthetic substances are used to impart odour to a perfume. For example, terpenoids like linalool which occur in essential oils are natural odour producing compounds, while anisaldelyde (p-methoxybenzaldehyde), is a synthetic odour producing compound. (3) Talcum powder : Talcum powder is used to reduce irritation of the skin. Talcum powders like face powders contain talc \[(M{{g}_{3}}{{(OH)}_{2}}S{{i}_{4}}{{O}_{10}}).\] Chalk, zinc oxide, zinc stearate and a suitable perfume act as the other main constituents of talcum powder. Often specific ingredients like antiseptic and cooling agents are added. The role of the talc is to act as a powder base and to make skin smooth. Chalk absorbs secretion (perspiration) without showing any evidence of such absorption. Zinc oxide masks enlarged pores and minor blemishes, whereas zinc stearate makes powder adhere to skin. Baby talcum powders contain considerable amounts of zinc stearate for adhesiveness and boric acid, for antiseptic purposes. Talcum powders need to be dusted with care to prevent inhalation of the fine particles, which irritate the lungs. (4) Deodorants : As the name suggests, deodorants are applied primarly to mask the body odour. The body odour results from the bacterial action following perspiration. A deodorant must therefore, possess anti-bacterial properties. Aluminium salts, have been found to possess excellent antibacterial properties. In addition to aluminium salts, \[ZnO,Zn{{O}_{2}}\] and more...

Catgeory: JEE Main & Advanced