In the following series of reactions identify the major products A & B respectively:
Electrophilic Aromatic Substitution
Electrophilic Aromatic Substitution

Solution & Explanation

### Related Formula Orienting effects in electrophilic aromatic substitution: - Bromine (-Br) is ortho/para-directing (para-dominated due to steric hindrance). - Sulfonic acid group (-SO_3H) is a strong deactivating, meta-directing group.
Electrophilic Aromatic Substitution
Electrophilic Aromatic Substitution
### Core Logic Analyzing the first step: - Sulfonation of bromobenzene with mathrmSO_3/mathrmH_2mathrmSO_4 yields 4-bromobenzenesulfonic acid as the major product (A) due to steric hindrance at the ortho-position. ### Step 1: Determine orientation for the second step In 4-bromobenzenesulfonic acid, we have two substituents: - -Br (ortho/para director) - -SO_3H (meta director) The positions meta to the deactivating -SO_3H group correspond to the positions ortho to the -Br group. Both directing effects align on the same position (carbon-3/carbon-5). Since -Br is activating relative to -SO_3H, it controls the orientation. ### Step 2: Identify Product B Halogenation with mathrmBr_2/mathrmFe introduces a bromine atom ortho to the existing bromine atom (meta to -SO_3H): textProduct B = text3,4-dibromobenzenesulfonic acid This matches Option (2). ### Pattern Recognition When an activating group (-Br) and a deactivating group (-SO_3H) compete on a benzene ring, the orienting influence of the activating group wins. Position ortho to the bromine atom is favored over meta positions of the sulfonic acid group. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Hydrocarbons Class 12 Chemistry: Haloalkanes and Haloarenes

More Hydrocarbons Previous-Year Questions — Page 5

Q84 jee_main_2024_31_jan_evening Halogenation of Alkanes (Isomers)
Number of isomeric products formed by mono-chlorination of 2-methylbutane in presence of sunlight is ________
Numerical Answer. Answer: 6 to 6

Solution

### Core Logic The structure of 2-methylbutane is CH_3-CH(CH_3)-CH_2-CH_3. It has four different types of hydrogen atoms, which can be substituted to form structural isomers: 1) 1-chloro-2-methylbutane: Chlorination at terminal CH_3 near branch. Yields a chiral center at C2 (2 enantiomers). 2) 2-chloro-2-methylbutane: Chlorination at the tertiary carbon (1 achiral product). 3) 2-chloro-3-methylbutane: Chlorination at the CH_2 group. Yields a chiral center at C2 (2 enantiomers). 4) 1-chloro-3-methylbutane: Chlorination at the far terminal CH_3. No chiral center (1 achiral product).
Halogenation of Alkanes (Isomers) diagram for Q84 - JEE Main 2024 Evening
Halogenation of Alkanes (Isomers) diagram for Q84 - JEE Main 2024 Evening
### Step 1: Counting Stereoisomers Total isomeric products = 2 (from 1st) + 1 (from 2nd) + 2 (from 3rd) + 1 (from 4th) = 6. ### Pattern Recognition When asked for "isomeric products" in halogenation without specifying "structural isomers", you must count stereoisomers (enantiomers) as well. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Hydrocarbons Class 12 Chemistry: Haloalkanes and Haloarenes
Q87 jee_main_2024_31_jan_morning Kolbe's Electrolysis
Number of alkanes obtained on electrolysis of a mixture of CH_3COONa and C_2H_5COONa is
Numerical Answer. Answer: 3 to 3

Solution

### Core Logic Kolbe's electrolytic method generates free radicals at the anode, which then combine to form alkanes. The given mixture yields two types of carboxylate radicals which decarboxylate to form alkyl radicals: CH_3COONa rightarrow dotCH_3 C_2H_5COONa rightarrow dotC_2H_5 These radicals can couple in three different ways: 1. Cross coupling: dotCH_3 + dotC_2H_5 rightarrow CH_3-CH_2-CH_3 (Propane) 2. Self-coupling 1: dotCH_3 + dotCH_3 rightarrow CH_3-CH_3 (Ethane) 3. Self-coupling 2: dotC_2H_5 + dotC_2H_5 rightarrow CH_3-CH_2-CH_2-CH_3 (Butane) Thus, a total of 3 different alkanes are formed. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Hydrocarbons
Rankbit System
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