Govt Exams
In Friedel-Crafts acylation, AlCl₃ facilitates the formation of the acetyl cation (CH₃CO⁺) from acetyl chloride. This electrophilic acylium ion then attacks the benzene ring.
The HNO₃/H₂SO₄ mixture generates NO₂⁺ (nitronium ion), which is the electrophile attacking the benzene ring in the rate-determining step. This is a classic electrophilic aromatic substitution.
The parent chain is butane (4 carbons). Numbering from the end nearest to substituent gives Br at position 2. IUPAC name is 2-bromobutane. Option D is a common name.
Peroxides initiate free radical mechanism (Kharasch effect). In free radical addition, HBr adds anti-Markovnikov to propene, giving 1-bromopropane as the major product. The Br radical adds first to the terminal carbon.
Dehydration of 2-methylbutan-2-ol follows Zaitsev's rule, producing the most stable (most substituted) alkene. 2-methylbut-2-ene is a trisubstituted alkene and is the major product.
Tollens test is positive for aldehydes. Propanal (CH₃CH₂CHO) is an aldehyde and gets oxidized to carboxylic acid, reducing Ag⁺ to Ag (silver mirror). Acetone is a ketone, ether and alcohol do not give positive test.
Phenol is highly activated towards electrophilic aromatic substitution due to the electron-donating -OH group. Bromine can add at all three ortho and para positions with excess bromine, giving 2,4,6-tribromophenol.
tert-Butyl bromide is a tertiary alkyl halide. Tertiary substrates preferentially undergo SN1 mechanism due to stable tertiary carbocation formation. SN2 is hindered by steric effects.
But-2-ene (CH₃-CH=CH-CH₃) on ozonolysis gives two identical fragments, each being acetaldehyde (CH₃CHO). The double bond cleaves symmetrically.
Hydroboration-oxidation follows anti-Markovnikov's rule and gives Markovnikov's hydration product after oxidation. 1-methylcyclohexene gives secondary alcohol, while pent-1-ene gives primary and 2-methylbut-2-ene gives tertiary alcohol.