Read the passage given below to answer questions:
Most of haloalkanes and haloarenes react with certain metals to give compound containing carbon metal bonds called organometallic compounds. Grignard reagent is such organomagnesium compound. Grignard reagent can be prepared from halogen derivative of alkanes/arenes with magnesium metal in dry ether. These are highly reactive compounds and react with source of proton to give hydrocarbon. Grignard reagents undergo addition with carbonyl compounds to give corresponding alcohols.
The number of alcohols which can be produced from Grignard reagent and formaldehyde from the following is
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 3
With formaldehyde the Grignard reagent always gives a primary alcohol, \( \ce{R-CH2OH} \):
\( \ce{RMgX + HCHO -> RCH2OMgX} \xrightarrow{\ce{H2O}} \ce{RCH2OH} \)
(1) Propan-1-ol, \( \ce{CH3CH2CH2OH} \) — primary; from \( \ce{CH3CH2MgX} \). Yes
(2) Butan-2-ol — secondary; needs an aldehyde other than HCHO. No
(3) The –OH is on a carbon carrying three alkyl groups — tertiary; needs a ketone. No
(4) 2-Methylpropan-1-ol, \( \ce{(CH3)2CHCH2OH} \) — primary; from \( \ce{(CH3)2CHMgX} \). Yes
(5) Benzyl alcohol, \( \ce{C6H5CH2OH} \) — primary; from \( \ce{C6H5MgX} \). Yes
Three alcohols, (1), (4) and (5), can be made.
NCERT (2026-27 edition):
From Grignard Reagents
