Question

1. Draw the structures of all isomeric alcohols of molecular formula C₅H₁₂O and give their IUPAC names.
2. Classify the isomers of alcohols in the above question as primary, secondary and tertiary alcohols.

Answer 1

1. The isomeric alcohols with molecular formula C₅H₁₂O are:
   1. \[\ce{\underset{Pentanol (1^\circ)}{CH3 - CH2 - CH2 - CH2 - CH2 - OH}}\]
   2. 
      \[\begin{array}{cc}
      \ce{CH3 - CH2 - CH2 - \overset{∗}{C}H - CH3}\\
      \phantom{....................}|\\
      \phantom{........................}\ce{\underset{Pentan-2-ol (2^\circ)}{OH}}\
      \end{array}\]
   3. 
      \[\begin{array}{cc}
      \ce{CH3 - CH2 - CH - CH2 - CH3}\\
      |\phantom{..}\\
      \phantom{..}\ce{\underset{Pentan-3-ol (2^\circ)}{OH}}\
      \end{array}\]
   4. 
      \[\begin{array}{cc}
      \ce{H3C - H2C - H\overset{∗}{C} - CH2OH}\\
      \phantom{.........}|\\
      \phantom{.............}\ce{\underset{2-Methylbutan-1-ol (1^\circ)}{CH3}}\
      \end{array}\]
   5. 
      \[\begin{array}{cc}
      \ce{CH3}\phantom{....................}\\
      |\phantom{........................}\\
      \ce{\underset{3-Methylbutan-1-ol (1^\circ)}{CH3 - CH - CH2 - CH2 - OH}}\\
      \end{array}\]
   6. 
      \[\begin{array}{cc}
      \ce{CH3}\phantom{.......}\\
      |\phantom{...........}\\
      \ce{CH3 - C - CH2 - CH3}\\
      |\phantom{............}\\
      \ce{\underset{2-Methylbutan-2-ol (3^\circ)}{OH}}\phantom{.........}\
      \end{array}\]
   7. 
      \[\begin{array}{cc}
      \ce{CH3}\phantom{.......}\\
      |\phantom{..........}\\
      \ce{CH3 - C - CH2 - OH}\\
      |\phantom{..........}\\
      \ce{\underset{2, 2-Dimethylpropan-1-ol (1^\circ)}{CH3}}\phantom{......}\
      \end{array}\]
   8. 
      \[\begin{array}{cc}
      \ce{CH3}\phantom{...}\ce{OH}\phantom{.}\\
      |\phantom{.........}|\phantom{...}\\
      \ce{\underset{3-Methylbutan-2-ol (2^\circ)}{CH3 - CH - \underset{∗}{C}H - CH3}}\
      \end{array}\]
      Isomers b, d and h contain chiral carbon atoms; thus, they exhibit enantiomerism.
2. Isomers a, d, e, and g are primary alcohols. 
   Isomers b, c and h are secondary alcohols.
   Isomer f is a tertiary alcohol.