Question

Amongst the following, the one which can exist in free state as a stable compound is:

• A. $C_7{H}_{9}O$
• B. $C_8{H}_{12}O$
• C. $C_6{H}_{11}O$
• D. $C_{10}{H}_{17}{O}_2$

Answer 1

Answer: (B)

$C_8{H}_{12}O$

Molecules having the whole number for a degree of unsaturation can exist in the free state as stable compounds

Degree of unsaturation $=\frac{\sum n(v-2)}{2}+1$

Where $n=$ number of atoms of a particular type $v=$ valency of the atom

(a) for $C_7{H}_{9}O$

$DU=\frac{7(4-2)+9(1-2)+1(2-2)}{2}+1=3.5$

(b) For $C_8{H}_{12}O$

$DU=\frac{8(4-2)+9(1-2)+1(2-2)}{2}+1=3.0$

(c) For $C_6{H}_{11}O$

$DU=\frac{6(4-2)+11(1-2)+1(2-2)}{2}+1=1.5$

(d) For $C_{10}{H}_{17}{O}_2$

$DU=\frac{10(4-2)+17(1-2)+2(2-2)}{2}+1=2.5$

$\therefore$ $C_8{H}_{11}O$ will exist in the free state or a stable compound

Hence, the correct option is $\text{B}$