A) 2, 5 dimethyl hexane
B) 2, 3, 4-trimethyl pentane
C) 2, 2, 4, 4-tetramethyl pentane
D) 2, 2, 3-trimethyl pentane
Correct Answer: B
Solution :
Key Idea: Only \[1\] alkyl group or \[C\] is attached to \[C-\]atom 2 alkyl group or \[C\] are attached to \[C-\]atom 3 alkyl group or \[C\] are attached to \[C-\]atom Draw structure of all compounds and count \[{{3}^{o}}C\] atoms [a]\[\underset{\text{2,5}\,\,\text{dimethyl}\,\,\text{hexane}}{\mathop{\underset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,-\underset{{{3}^{o}}}{\overset{\underset{|}{\mathop{^{{{1}^{o}}}C{{H}_{3}}}}\,}{\mathop{CH}}}\,-\underset{{{2}^{o}}}{\mathop{C{{H}_{2}}}}\,-\underset{{{2}^{o}}}{\mathop{C{{H}_{2}}}}\,-\underset{{{3}^{o}}}{\overset{\underset{|}{\mathop{^{{{1}^{o}}}C{{H}_{3}}}}\,}{\mathop{CH}}}\,-\underset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,}}\,\] [b]\[\underset{\text{2,3,4-trimethyl}\,\,\text{pentane}}{\mathop{\overset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} ^{{{1}^{o}}}C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{^{{{3}^{o}}}C}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} {{1}^{o}} \\ C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{{{C}^{{{3}^{o}}}}}}}\,-\underset{\begin{smallmatrix} | \\ H \end{smallmatrix}}{\overset{\begin{smallmatrix} CH_{3}^{{{1}^{o}}} \\ | \end{smallmatrix}}{\mathop{{{C}^{{{3}^{o}}}}}}}\,-\overset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,}}\,\] [c]\[\underset{\text{2,2,4,3-tetramethyl}\,\text{pentane}}{\mathop{\overset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,-\underset{\begin{smallmatrix} | \\ C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} ^{{{1}^{o}}}C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{{{C}^{{{4}^{o}}}}}}}\,-\overset{{{1}^{o}}}{\mathop{C}}\,{{H}_{2}}-\underset{\begin{smallmatrix} |\,\,{{1}^{o}} \\ C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} {{1}^{o}} \\ CH \\ | \end{smallmatrix}}{\mathop{{{C}^{{{4}^{o}}}}}}}\,-\overset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,}}\,\] [d]\[\underset{2\text{,}\,\,\text{2,}\,\,\text{3-trimethyl}\,\,\text{pentane}}{\mathop{\overset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,-\underset{\begin{smallmatrix} |{{1}^{o}} \\ C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} ^{{{1}^{o}}}C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{{{C}^{{{4}^{o}}}}}}}\,-\underset{{{3}^{o}}}{\overset{\begin{smallmatrix} {{1}^{o}} \\ C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{CH}}}\,-\underset{{{2}^{o}}}{\mathop{C{{H}_{2}}}}\,-\underset{{{1}^{o}}}{\mathop{C{{H}_{3}}}}\,}}\,\] \[\therefore \]2, 3, 4-trimethyl pentane has highest number of\[{{3}^{o}}\]carbon atoms
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