Camphor is a ketone compound and is one of the active ingredients in vicks products. if camphor has m+ = 152 and contains 1 double bond(s) and 2 ring(s); what is its molecular formula?

           C₁₀H₁₆O

Explanation:

                   Molecular formula can be determined from parent peak by using rule of thirteen.

Rule of Thirteen:

First divide the parent peak value by 13 as,

                 = 152 ÷ 13

                 = 11.69

Now, multiply 13 by 11,

                 = 13 × 11 (here, 11 specifies number of carbon atoms)

                 = 143

Now subtract 143 from 152,

                 = 152 - 143

                 = 9

Add 9 into 11,

                 = 9 + 11

                 = 20 (hydrogen atoms)

So, the rough formula we have is,

                                                        C₁₁H₂₀

Now, add one Oxygen atom to above formula and subtract one Carbon and 4 Hydrogen atoms as these numbers are equal to atomic mass of Oxygen atom as,

                 C₁₁H₂₀   -------O-------->    C₁₀H₁₆O

Calculate Hydrogen deficiency index as,

                 HDI  =  (2x + 2 - y) / 2

where,

x = C atoms

y = H atoms

                 HDI  =  [2(10) + 2 - 16] / 2

                 HDI  =  (20 + 2 - 16) / 2

                 HDI  =  (22-16) / 2

                 HDI  =  6 / 2

                 HDI  =  3

It means, Camphor contains 1 double bond and two rings. As, HDI of double bond is 1 and HDI of one ring is 1.