In keto-enol tautomerism of dicarbonyl compounds, the enol-form is preferred in contrast to the keto-form, this is due to

• presence of carbonyl group on each side of -CH₂ group

• resonance stabilisation of enol form

• presence of methylene group

• rapid chemical exchange

In the cannizzaro reaction given below, the slowest step is

2Ph - CHO $\stackrel{{\mathrm{OH}}^{-}}{\to }$ Ph - CH₂ - OH + PhCO${}_2^{-}$

• the attack of OH^- at the carbonyl group

• the transfer of hydride ion to the carbonyl group

• the abstraction of a proton from the carboxylic acid

• the deprotonation of Ph - CH₂OH

Which of the following pairs give positive Tollen's test?

• Glucose, sucrose

• Glucose, fructose

• Hexanal, acetophenone

• Fructose, sucrose

Which of the following isomerism is shown by ethyl acetoacetate?

• Geometrical isomerism

• Keto-enol tautomerism

• Enantiomerism

• Diastereoisomerism

Ketones [R - $\underset{\mathrm{O}}{\underset{\left|\right|}{\mathrm{C}}}$ - R'] where, R = R' = alkyl group can be obtained in one step by

• hydrolysis of esters

• oxidation of primary alcohols

• oxidation of secondary alcohols

• reaction of acid halide with alcohols

56.

An optically active compound 'X' has molecular formula C₄H₈O₃. It evolves CO₂ with aqueous NaHCO₃. 'X' reacts with LiAlH₄ to give an achiral compound. 'X' is

• CH₃CH₂C(OH)HCOOH

• CH₃C(OMe)HCOOH

• CH₃CH(CH₂OH)HCOOH

• CH₃C(OH)HCH₂COOH

Out of H₂S₂O₃, H₂S₂O₄, H₂SO₅ and H₂S₂O₈ peroxy acids are

• H₂S₂O₃; H₂S₂O₈

• H₂SO₅; H₂S₂O₈

• H₂S₂O₄; H₂SO₅

• H₂S₂O₃; H₂S₂O₄

In a Claisen condensation reaction (when an ester is treated with a strong base)

• a proton is removed from the α-carbon to form a resonance stabilised carbanion of the ester

• carbanion acts as a nucleophile in a nucelophilic acyl substitution reaction with another ester molecule

• a new C - C bond is formed

• All of the above statements are correct

An organic compound B is formed by the reaction of ethyl magnesium iodide with a substance A, followed by treatment with dilute aqueous acid. Compound B does not react with PCC or PDC in dichloromethane. Which of the following is a possible compound for A?

• 

• CH₃CH₂COCH₃

• CH₃COH

• H₂C=O

CH₃COCH₂CH₂COOCH₂CH₃ $\underset{\left(\mathrm{ii}\right) {\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\left(\mathrm{i}\right) {\mathrm{CH}}_3\mathrm{MgBr} (\mathrm{one} \mathrm{mole})}{\to }}$ A

A formed in this reaction is