Question

Question: Draw a structure for a carboxylic acid that has a molecular ion with an m/zvalue of 116.

Short answer

Answer

The possible structures are given below.

Step-by-step solution

Nitrogen rule

According to nitrogen rule, an organic compound with odd molar mass contain odd number of nitrogen atoms, and compound with even molar mass contain even number of nitrogen atoms.

Identify the molecular formula for carboxylic acid

High resolution mass spectrometry calculates exact mass of the fragments up to 5 ppm level.

It is given, M⁺=116

Consider mass of carboxylic acid as 116.

The given mass is 116, which is even. It means that camphor molecule contain zero or even number of nitrogen atoms, according to nitrogen rule.

According to rule of 13, divide 116 by 13

The remainder is 12. The basic C-H formula is:C_nH_n+1

Here n=8 and r=12

(n= quotient, r=remainder)

C₈H₈₊₁₂ = C₈H₂₀

Thus, the base value is C₈H₂₀ .

It contains zero nitrogen atoms because mass number is even. So, according to nitrogen rule, zero or even nitrogen is added to the compound.

Because the carbonyl compound contains two oxygens, therefore, two Os must be added to the base value and two Cs and 8H must be subtracted.

Therefore, the molecular formula becomes:C₈H₂₀ - 2CH₄ +20 = C₆H₁₂O₂

Determining Double Bond equivalent (DBE)

Degree of unsaturation is also known as double bond equivalent (DBE). If molecular formula is given, plug in the number into this formula.

$DBE=\frac{2C+2+N-X-H}{2}$

Where, C is the number of Carbon

N is the number of nitrogen

H is the number of hydrogen

X is the number of halogen

ForC₆H₁₂O₂