Question 1

n-Butane on monochlorination under photochemical condition gives an optically active compound "P". "P" on further chlorination gives dichloro compounds. The number of dichloro compounds obtained (igno

Accepted Answer

The structure of n-butane is CH_3-CH_2-CH_2-CH_3. Monochlorination of n-butane gives two structural isomers: 1-chlorobutane and 2-chlorobutane. Among these, 2-chlorobutane (CH_3-CH_2-C^ * HCl-CH_3) contains a chiral carbon atom and is optically active. Thus, the optically active compound "P" is 2-chlorobutane. Further chlorination of 2-chlorobutane can take place at any of the four carbon atoms, yielding the following dichloro compounds (ignoring stereoisomers): 1. Chlorination at C-1: CH_3-CH_2

Question 2

Given below are two statements: Statement I: Due to increase in van der Waals forces, the order of boiling points is CH_3CH_2CH_2I > CH_3CH_2I > CH_3I. Statement II: As para-dichlorobenzene is more sy

Accepted Answer

Statement I is true because as the size of the alkyl group increases, the molecular mass and surface area increase. This leads to an increase in the magnitude of van der Waals forces, which in turn increases the boiling point. Thus, the correct order of boiling points is CH _3 CH _2 CH _2 I > CH _3 CH _2 I > CH _3 I . Statement II is true because para-dichlorobenzene is more symmetrical than ortho-dichlorobenzene, allowing it to pack more efficiently in the crystal lattice, which results in a hi

Question 3

RMgI when treated with ice cold water liberated a gas which occupied 1.4 dm ^3/ g at STP. The gas produced is further reacted with iodine in presence of HIO_3 to give compound (X). Compound (X) in pre

Accepted Answer

The reaction of Grignard reagent with water yields an alkane: RMgI + H_2O RH + Mg(OH)I Given that 1 g of the gas RH occupies 1.4 dm ^3 at STP, we can find its molar mass. Using the standard molar volume at STP (22.4 dm ^3): Molar mass of RH = 22.4 dm ^3 mol ^ -1 1.4 dm ^3 g ^ -1 = 16 g mol ^ -1 The alkane with a molar mass of 16 g mol ^ -1 is methane (CH_4). Methane reacts with iodine in the presence of an oxidizing agent like HIO_3 (which prevents the backward reaction by consuming the formed H

Question 4

Benzyl isocyanide can be obtained from Choose the correct answer from the options given below:

Accepted Answer

Reaction A: C_6H_5CH_2Br + AgCN C_6H_5CH_2NC + AgBr AgCN is predominantly covalent, so the nucleophilic attack occurs through the nitrogen atom, forming benzyl isocyanide. Reaction B: C_6H_5CH_2NH_2 + CHCl_3 + 3NaOH C_6H_5CH_2NC + 3NaCl + 3H_2O This is the carbylamine reaction. Primary amines react with chloroform and alkali to form isocyanides. Benzyl amine gives benzyl isocyanide. Reaction C: C_6H_5Br + AgCN No reaction Aryl halides are generally unreactive towards nucleophilic substitution un

Question 5

Match the LIST-I with LIST-II List-I (Reaction) List-II (Mechanism) A. Williamson Synthesis I. Electrophilic addition B. Friedel Craft Reaction II. Free radical substitution C. Bromination of vinyl be

Accepted Answer

Williamson synthesis involves the reaction of an alkyl halide with a sodium alkoxide to form an ether, which proceeds via a nucleophilic substitution (S_N2) mechanism. Thus, A matches with III. Friedel-Crafts reaction involves the alkylation or acylation of an aromatic ring in the presence of a Lewis acid catalyst, which proceeds via an electrophilic substitution mechanism. Thus, B matches with IV. Bromination of vinyl benzene (styrene) involves the addition of bromine across the carbon-carbon d

Question 6

Match the LIST-I with LIST-II List-I Name of reaction List-II Reagent or catalyst used A. Finkelstein reaction I. SbF_3 B. Swarts reaction II. Na, dry ether C. Sandmeyer's reaction III. NaI D. Fittig

Accepted Answer

Finkelstein reaction involves the conversion of alkyl chlorides or bromides to alkyl iodides using NaI in dry acetone. Thus, A matches with III. Swarts reaction is used for the synthesis of alkyl fluorides by heating an alkyl chloride or bromide in the presence of a metallic fluoride such as SbF_3, AgF, Hg_2F_2, or CoF_2. Thus, B matches with I. Sandmeyer's reaction involves the conversion of aryl diazonium salts to aryl halides using cuprous halides like Cu_2Cl_2 or Cu_2Br_2. Thus, C matches wi

Question 7

Correct statements regarding alkyl halides (R - X) among the following are: A. Alcohol being less polar solvent as compared to water, alcoholic KOH favours elimination reaction with R - X. B. Order of

Accepted Answer

Statement A is correct. Alcoholic KOH provides alkoxide ions which are stronger bases than hydroxide ions. Furthermore, alcohol is a less polar solvent than water, which decreases the solvation of the base, making it more effective for elimination reactions over substitution. Statement B is incorrect. The reactivity towards the S_N^1 mechanism depends on the stability of the intermediate carbocation. The carbocation C_6H_5- + C H-C_6H_5 is more stable than C_6H_5- + C H_2 due to extended resonan

Question 8

Given below are two statements : Statement (I) : Benzyl chloride reacts faster in S_N1 mechanism than ethyl chloride. Statement (II) : Ethyl carbocation intermediate is less stabilized by hyperconjuga

Accepted Answer

The rate of S_N1 reaction depends on the stability of the carbocation intermediate formed during the rate-determining step. Benzyl chloride undergoes ionization to form a benzyl carbocation (C_6H_5CH_2^+), whereas ethyl chloride forms an ethyl carbocation (CH_3CH_2^+). The benzyl carbocation is highly stabilized by the delocalization of the positive charge over the benzene ring through resonance. On the other hand, the ethyl carbocation is stabilized only by hyperconjugation involving three -hyd

Question 9

Which of the following reaction is NOT correctly represented?

Accepted Answer

Reaction (1): Toluene + Br_2/Fe in dark conditions undergoes electrophilic aromatic substitution on the benzene ring, producing ortho and para bromotoluenes. This is correctly represented. Reaction (2): The diazonium salt reacts with Cu_2Br_2/HBr via the Sandmeyer reaction to produce bromobenzene. This is correctly represented. Reaction (3): Toluene + Br_2 with light (h ) undergoes free radical substitution at the benzylic position, producing benzyl bromide (CH₂Br). This is correctly represented

Question 10

Grignard reagent RMgBr ( P ) reacts with water and forms a gas (Q). One gram of Q occupies 1.4 dm ^ 3 at STP. (P) on reaction with dry ice in dry ether followed by H _ 3 O ^ + forms a compound (Z). 0.

Accepted Answer

Grignard reagent RMgBr reacts with water to produce gas Q. One gram of Q occupies 1.4 L at STP. Moles of Q = 1.4/22.4 = 0.0625 mol, so molar mass = 1/0.0625 = 16 g/mol, identifying Q as CH₄. Thus P = CH₃MgBr. When P reacts with dry ice: CH _3 MgBr + CO _2 CH _3 COOMgBr . Upon treatment with H₃O⁺, this gives Z = CH₃COOH (acetic acid). Molar mass of Z = 60 g/mol. Mass of 0.1 mol = 0.1 × 60 = 6 g.

Question 11

Given below are two statements: Statement I : ' C - Cl ^ bond is stronger in CH _ 2 = CH - Cl than CH _ 3 - CH _ 2 - Cl Statement II : The given optically active molecule, on hydrolysis gives a soluti

Accepted Answer

Statement I: In vinyl chloride (CH₂=CH-Cl), the C-Cl bond involves an sp² hybridized carbon, while in ethyl chloride (CH₃-CH₂-Cl), it involves an sp³ carbon. The sp² carbon has greater s-character, forming a shorter and stronger C-Cl bond. Additionally, resonance stabilization from the Cl atom's p-orbital overlapping with the π system further strengthens the vinyl C-Cl bond. Statement I is TRUE. Statement II: The optically active molecule shown has a stereogenic center bearing Me, Ph, Et, and Cl

Question 12

Match the LIST-I with LIST-II List-I (Chloro derivative) List-II (Example) A. Vinyl Chloride I. CH_2 = CH - CH_2Cl B. Benzyl chloride II. CH_3 = CH(Cl)CH_3 C. Alkyl chloride III. CH_2 = CHCl D. Allyl

Accepted Answer

Vinyl Chloride has Cl directly attached to a C=C double bond, matching III: CH₂=CHCl. Benzyl Chloride has CH₂Cl attached to a benzene ring, matching IV (benzene with CH₂Cl substituent). Alkyl Chloride is a general chlorine-substituted alkane, matching II: CH₂-CH(Cl)CH₃ (a standard secondary alkyl chloride). Allyl Chloride has CH₂Cl attached to the allylic position (adjacent to C=C), matching I: CH₂=CH-CH₂Cl. The correct matching is A-III, B-IV, C-II, D-I.

Question 13

Consider all the structural isomers with molecular formula C _ 5 H _ 11 Br are separately treated with KOH ( aq ) to give respective substitution products, without any rearrangement. The number of pro

Accepted Answer

For C₅H₁₁Br structural isomers to show optical isomerism after KOH substitution (Br→OH), the resulting product must have a chiral center (asymmetric carbon with four different groups). Possible carbon skeletons: n-pentane, 2-methylbutane, 2,2-dimethylpropane. Analysis of isomers: 2-bromopentane → CH₃CHOHCH₂CH₂CH₃: C2 bonded to H, OH, CH₃, and CH₂CH₂CH₃ (chiral). 3-bromopentane → CH₃CH₂CHOHCH₂CH₃: C3 bonded to H, OH, CH₂CH₃, CH₂CH₃ (NOT chiral). 3-bromo-2-methylbutane → CH₃CH(CH₃)CHOHCH₃: Chiral

Question 14

The correct order of the rate of reaction of the following reactants with nucleophile by SN1 mechanism is: (Given : Structure I and II are rigid)

Accepted Answer

Rate of S_N1 Stability of C^ formed (I) and (II) are unstable due to Bredt's rule, (I) has more +I effect. (II) < (I) < (III) < (IV)

Question 15

As compared with chlorocyclohexane, which of the following statements correctly apply to chlorobenzene? A. The magnitude of negative charge is more on chlorine atom. B. The C - Cl bond has partial dou

Accepted Answer

Chlorobenzene has Cl attached to an sp² carbon of the benzene ring, while chlorocyclohexane has Cl attached to an sp³ carbon. Statement B is correct: the C-Cl bond has partial double bond character due to resonance with the aromatic π system, where chlorine's lone pairs interact with the aromatic ring. Statement C is correct: the C-Cl bond is less polar in chlorobenzene because the resonance contribution reduces the electronegativity difference between C and Cl. Statement E is correct: the C-Cl

Question 16

The correct order of reactivity of CH _ 3 Br in methanol with the following nucleophiles is F ^ - , I ^ - , C _ 2 H _ 5 O ^ - and C _ 6 H _ 5 O ^ -

Accepted Answer

In methanol (protic solvent), nucleophilicity is determined by basicity and solvation effects. Smaller ions are heavily solvated by the protic solvent, reducing their effective nucleophilicity. C₂H₅O⁻ (ethoxide) is the strongest nucleophile as it is less solvated and highly basic. C₆H₅O⁻ (phenoxide) is weaker due to resonance stabilization by the benzene ring. F⁻ is highly solvated despite high basicity, reducing its nucleophilicity significantly. I⁻ is the best nucleophile because it is the lar

Question 17

The correct order of the rate of the reaction for the following reaction with respect to nucleophiles is : CH _ 3 Br + Nu ^ CH _ 3 Nu + Br ^

Accepted Answer

For the SN2 reaction CH₃Br + Nu⁻, nucleophilicity in aprotic solvents is determined by basicity and polarizability. ⁻OH (hydroxide) is the strongest nucleophile and base, making it highly reactive. PhO⁻ (phenoxide) is a good nucleophile with reasonable basicity. CH₃COO⁻ (acetate) is weakened by resonance stabilization of its negative charge across the C-O bonds, reducing its nucleophilicity. ClO₄⁻ (perchlorate) is a very weak nucleophile, being the conjugate base of a strong acid (HClO₄). The co

Question 18

The correct order of reactivity of the following benzyl halides towards reaction with KCN is :

Accepted Answer

Reactivity in SN2 reactions with KCN depends on the stability and nucleophilicity of the transition state. For benzyl halides, substituents on the benzene ring affect the reactivity of the benzylic carbon through resonance and inductive effects. Para-nitro group (-NO2) is strongly electron-withdrawing, activating the benzylic carbon toward nucleophilic substitution. Para-amino (-NH2) is electron-donating, deactivating. Para-hydroxyl (-OH) is weakly donating. Meta-nitro group has reduced electron

Haloalkanes and Haloarenes — Previous Year Questions & Solutions