Question 2 of 32intermediate🔧 ApplyShort Answer3 marks

Write structures of different isomeric alkyl groups corresponding to the molecular formula C₅H₁₁. Write IUPAC names of alcohols obtained by attachment of –OH groups at different carbons of the chain.

Correct Answer

The eight isomeric alkyl groups for the molecular formula C5H11C_5H_{11} and their corresponding alcohols are:

(i) CH3−CH2−CH2−CH2−CH2−CH_3 - CH_2 - CH_2 - CH_2 - CH_2 - gives CH3−CH2−CH2−CH2−CH2−OHCH_3 - CH_2 - CH_2 - CH_2 - CH_2 - OH (Pentan-1-ol) (ii) CH3−CH−CH2−CH2−CH3CH_3 - CH - CH_2 - CH_2 - CH_3 gives CH3−CH(OH)−CH2−CH2−CH3CH_3 - CH(OH) - CH_2 - CH_2 - CH_3 (Pentan-2-ol) (iii) CH3−CH2−CH−CH2−CH3CH_3 - CH_2 - CH - CH_2 - CH_3 gives CH3−CH2−CH(OH)−CH2−CH3CH_3 - CH_2 - CH(OH) - CH_2 - CH_3 (Pentan-3-ol) (iv) CH3−CH(CH3)−CH2−CH2−CH_3 - CH(CH_3) - CH_2 - CH_2 - gives CH3−CH(CH3)−CH2−CH2−OHCH_3 - CH(CH_3) - CH_2 - CH_2 - OH (3-Methylbutan-1-ol) (v) CH3−CH2−CH(CH3)−CH2−CH_3 - CH_2 - CH(CH_3) - CH_2 - gives CH3−CH2−CH(CH3)−CH2−OHCH_3 - CH_2 - CH(CH_3) - CH_2 - OH (2-Methylbutan-1-ol) (vi) CH3−C(CH3)2−CH2−CH3CH_3 - C(CH_3)_2 - CH_2 - CH_3 gives CH3−C(OH)(CH3)−CH2−CH3CH_3 - C(OH)(CH_3) - CH_2 - CH_3 (2-Methylbutan-2-ol) (vii) (CH3)3C−CH2−(CH_3)_3C - CH_2 - gives (CH3)3C−CH2OH(CH_3)_3C - CH_2OH (2,2-Dimethylpropan-1-ol) (viii) (CH3)2CH−CH(CH3)−(CH_3)_2CH - CH(CH_3) - gives (CH3)2CH−CH(OH)−CH3(CH_3)_2CH - CH(OH) - CH_3 (3-Methylbutan-2-ol)

Exercise: Problem 9.2 | Q: 9.2 | (Page Page 4)
For More Understanding

Explanation

Alkyl groups are derived from alkanes by the removal of one hydrogen atom, having the general formula CnH2n+1C_nH_{2n+1}. For the C5H11C_5H_{11} group, there are eight possible structural isomers. By attaching a hydroxyl (−OH-OH) group to the free valence of each isomeric alkyl group, we obtain the corresponding isomeric alcohols, which are named according to IUPAC nomenclature rules.

Solution Steps

  1. Step 1: Identify the straight-chain alkyl group CH3CH2CH2CH2CH2−CH_3CH_2CH_2CH_2CH_2- and attach −OH-OH to get Pentan-1-ol.

  2. Step 2: Identify the branched-chain alkyl groups by varying the position of the methyl substituent and the free valence.

  3. Step 3: Attach the −OH-OH group to the free valence of each of the eight isomeric C5H11C_5H_{11} groups and write their respective IUPAC names: Pentan-2-ol, Pentan-3-ol, 3-Methylbutan-1-ol, 2-Methylbutan-1-ol, 2-Methylbutan-2-ol, 2,2-Dimethylpropan-1-ol, and 3-Methylbutan-2-ol.

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