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11127

Permanent polarization of sigma bond electrons of carbon chain due to electronegative difference of the atom attached at the end of the chain is known as inductive effect. It is of two types +I when the atom at the end of chain is less electronegative than carbon; and ?I when the atom attached at the end is more electronegative than carbon. It is an important effect.

Applications are :1. Expalining stability of reaction intermediates, 2. Relative strength of acids, 3. Relative strengths of bases, 4. Relative strengths of alkynes.

10176

Each purine base forms a stable hydrogen bonded pair with a specific pyrimindine base. Guanine forms a base pair with three hydrogen bonds to cytosine, and adenine forms a base pair with two hydrogen bonds to thymine ( or uracil in RNA).

DNA contains two complementary polynucleotide chains held together by hydrogen bonds between paired bases. Two strands are antiparallel. One strand is arranged 3?®5? from left to right, while the other runs in the opposite direction, 5?®3? from left to right.

The two complementory strands of DNA are coiled into helical conformation of about 20A⁰ in diameter, with both chains coiled around the same axis. The helix makes a complete turn for every ten residues, or about one turn in every 34A⁰ of length.

According to Erwin Chargaff?s rule, DNA contains equimolecular amounts of guanine & cytosine, and also equimolecular amounts of adenine & thymine.

Thus AG/TC ratio remains constant, only in genetic mutation it can be changed.

For details you can refer to molecular biology expert.

10590

Carbon atom can undergo three types of hybridization.

Sp³ or tetrahedral involving one s and three p orbitals.

Sp² or trigonal involving one s and two p orbitals.

Sp or diagonal involving one s and one p orbital.

Using these orbitals carbon atom forms single, double and triple bonds respectively.

Refer to study material, above mentioned sites for diagrammatic representation

The compounds mentioned may not undergo intramolecular dehydration, i.e., dehydration within the same molecule, e.g., alcohols form alkene by dehydration.

Two moles of acetic acid eliminate water to form acetic anhydride.

Please check the question again.

10548

In aminophenol the ring is activated due to the presence of electron donating groups. Carboxylic acid group is a ring deactivator, so in benzoic acid the ring is deactivated . Hence the order of reactivity should be Aminophenol > Benzene > Benzoic acid.

10483

For E² reaction the preferred conformation is anti. Hence in this reaction the hydrogen atom on the third carbon atom will have anti hydrogen available w.r.t. bromine, thus the product will be 3-phenylcyclopentene.

Similar reaction for has been studied for cyclohexane. Trans-2-methylbromocyclohexane gives 3-methylcyclohexene (cis isomer) by elimination reaction. Both C-H & C-X must be axial.

10480

The decreasing order of the rate of above reaction with nucleophile will be

RO ^- > ^- OH > C₆H₅O^- > RCOO ^?

Stronger the acid weaker is its conjugate base.

However in case of protic solvent this order may slightly change to ^?OH> CH₃O^-

10479

The attraction of the positive end of a molecular dipole for the negative end of another dipole may be called dipole-dipole interaction.

In case of benzene and carbontetrachloride dipole moment is zero. Only in case of acetone & acetonitrile dipole-dipole interaction will be possible.

(CH₃)₂C^d+=O ^d-??^d+CH₃CN ^d-

10478

Relative reactivities of aldehydes and ketones in nucleophilic addition reactions depend on

1.Steric hinderance : Larger the R and R? groups in the carbonyl compound, greater would be the magnitude of steric hinderance in the transition state and hence less reactive should be the carbonyl compound in nucleophilic addition.

2.Electronic factors: The alkyl groups release electrons and destabilize the transition state by intensifying the negative charge on carbonyl oxygen. Since aldehydes contain one & ketones contain two such groups, destabilization of transition state from a ketone would be much greater than that resulting from aldehydes.

Aromatic aldehydes & ketones are less reactive than corresponding aliphatic analogues due to +R effect of benzene ring which increases electron density on carbonyl carbon thereby repelling the nucleophile. Thus the order of reactivity would be

HCHO > CH₃COCH₃ > PhCOCH₃ > PhCOPh

10348

Amino acids with one amino and one carboxylic acid group are neutral; with two amino & one carboxylic acid group are basic ; with one amino & two carboxylic acid group are acidic.

Refer to your study material for structures of these amino acids, from which you will be able select correct statement.

10239

Waldon inversion occurs at a tetrahedral carbon atom during an S_N² reaction when the entry of the reagent and the departure of the leaving group are synchronous. The result is an inversion of configuration at the center of attack.

Refer to mechanism of S_N² reaction, backside attack by nucleophile, transition state in which attacking group-the carbon atom attacked ?and the leaving group are in a line.

10308

Nucleophilicity is the ability of a reagent to donate a pair of electrons to the carbon atom. The greater the nucleophilicity, the more rapid should be its S_N² reaction.

1.Nucleophilicity increases with increasing negative charge on the atom e.g., OH^-> H₂O

2.It increases with increasing atomic number down a group in the periodic table, thus

I^- > Br ^- >Cl ^- > F^-in a protic polar solvent.

3.It decreases with increasing atomic number along a period in the periodic table

C^- > N ^-> O ^- > F ^?

4.Conjugate base of a weaker acid is a stronger base.

Order of acidity is NH₃ < H₂O <CH₃OH < CH₃COOH

Order of basicity is NH₂^- > OH ^- > CH₃O ^- > CH₃COO ^?

10311

CH₃C(=O)OH + S(=O)Cl₂ ® CH₃C(=O)Cl + SO₂ + HCl

Structures of reactants not appearing on screen.

Prim H are attached to prim.carbon-the carbon which is attached to only one other carbon. so you can easily workout.

In organic chemistry we often use the terms monomer,dimer,trimer,tetramer and then polymer.For a substance to be a plymer its molar mass must be above 10000, larger number of monomer units linked together is a polymer.

Sucrose is a carbohydrate. carbohydrates are classified as monosaccharides-containing only one unit,further hydrolysis not possible; disaccharides-onhydrolysis give two monosaccharides; trisaccharides-give three; tetrasaccharides on hydrolysis give four; polysaccharides on hydrolysis give large number of monosaccharides.

Di,tri,tetra again grouped as oligosaccharides-many times considered from two to seven mono units on hydrolysis.

In this light we cannot call sucrose as polymer.