Haloalkanes And Haloarenes

Photochemical chlorination involves the substitution of hydrogen atoms with chlorine in the molecule. The number of isomeric monochlorides formed depends on the number of distinct hydrogen atoms in the molecule.

For 2-methylbutane, the possible sites for chlorination are at four positions:
1. The 1-position on the main chain
2. The 2-position on the main chain
3. The 3-position on the main chain
4. The methyl group attached at position 2

This gives four distinct monochlorides. In contrast, other molecules like 2-methylpropane and propane do not have enough distinct sites to give four different monochlorides.

The correct option is (C) : 2-Methylbutane

Reaction i: Wurtz Reaction

The reaction involves ethyl bromide (CH3-CH2-Br) reacting with sodium (Na) in dry ether. This is the Wurtz reaction, a coupling reaction where two alkyl halides react with sodium to form a new carbon-carbon bond, creating a longer alkane.

The general reaction is: 2 R-X + 2 Na → R-R + 2 NaX. In our case, R is ethyl (CH3-CH2) and X is bromine (Br). Therefore, the product will be CH3-CH2-CH2-CH3, which is butane.

Reaction ii: Decarboxylation

The reaction involves sodium acetate (CH3COONa) reacting with sodium hydroxide (NaOH) in the presence of calcium oxide (CaO) and heat (Δ). This is a decarboxylation reaction, where a carboxylic acid (or its salt) loses carbon dioxide (CO2) to form an alkane.

The general reaction is: R-COONa + NaOH → R-H + Na2CO3. In our case, R is methyl (CH3). Therefore, the product will be CH4, which is methane.

Therefore, the correct answer is (E) i) CH3-CH2-CH2-CH3 and ii) CH4

Reaction Steps:

Formation of Grignard Reagent (Compound 1): The reaction of methyl bromide (CH3Br) with magnesium (Mg) in dry ether forms a Grignard reagent. A Grignard reagent has the general formula R-MgX, where R is an alkyl or aryl group and X is a halogen. In this case, R is methyl (CH3) and X is bromine (Br). So compound 1 is methylmagnesium bromide (CH3MgBr).

Grignard Reaction with a Ketone followed by Acid Workup (Compound 2): The Grignard reagent (CH3MgBr) acts as a strong nucleophile and attacks the carbonyl carbon of the ketone. This forms a new C-C bond. The subsequent acid workup (H3O+) protonates the alkoxide intermediate, resulting in an alcohol.

The ketone structure present will have two methyl groups on one side of the carbonyl, so it will become a 2 degree alcohol after being reacted with the Grignard and then protonated.

Therefore, the correct answer is (C) CH3MgBr and

a) Grignard reagent:

• Characteristic example:
• Matches with (iv)

b) Sandmeyer's reaction:

• Uses catalysts
• Matches with (iii)

c) Cannizzaro reaction:

• Base-catalyzed ( )
• Matches with (v)

d) Friedel-Crafts reaction:

• Uses catalyst
• Matches with (i)

e) Wurtz reaction:

• Uses sodium metal
• Matches with (ii)

Correct Matching: a-(iv), b-(iii), c-(v), d-(i), e-(ii)

Thus, the correct option is (E): a) - (iv); b) - (iii); c) - (v); d) - (i); e) - (ii).