question_answer

Which of the following will have a \[meso-\]isomer also?

A)  2-chlorobutane

B)  2, 3-dichlorobutane

C)   2, 3-dichloropentane

D)   2-hydroxypropanoic acid

Correct Answer: B

Solution :

[a]\[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\overset{*}{\mathop{C}}}\,H-C{{H}_{2}}C{{H}_{3}}\] One asymmetric carbon atom, forms \[d-\] and \[l-\]optical isomers. Meso due to internal compensation [b] Two asymmetric carbon atoms, forms \[d-,\,\,l-\]and meso forms. [c]\[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\overset{*}{\mathop{C}}}\,H-\underset{\begin{smallmatrix}  | \\  Cl \end{smallmatrix}}{\overset{*}{\mathop{C}}}\,H-C{{H}_{2}}C{{H}_{3}}\] Two asymmetric carbon atoms but does not have symmetry. Hence, meso form is not formed. [d]\[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  OH \end{smallmatrix}}{\overset{*}{\mathop{C}}}\,H-COOH\] One asymmetric carbon atom, meso form is not formed.