Q 59P - Organic Chemistry (Mcmurry)

Question

Question:  The mass spectrum and ${}^{13}C$ NMR spectrum of a hydrocarbon are shown. Propose a structure for this hydrocarbon, and explain the spectral data.

Step-by-Step Solution

Answer

Structure of the compound is 3-hexene

                   $C{H}_{3}C{H}_{2}CH=CHC{H}_{2}C{H}_3$

Step-by-Step Solution Step 1: Mass spectra

It is a spectra used to determine the molecular mass of the compound and the structure by plotting the ion signal plot as a function of mass to charge ratio.

Step 2: Identify compound from mass spectra

The peak of the mass spectra at the mass to charge ratio is the 84 so, that must be the molecule ion peak per the molecular formula of the compound have a double bond or a ring and the base peak is at the 55 which is the loss of the methyl group

Step 3: C 13   NMR

Carbon-13 nuclear magnetic resonance is a technique similar to the NMR which is used to identify the carbon from the organic molecules or from the organometallic compounds like hydrogen is detected in NMR but it’s only sensitive to carbon-13, not carbon-12.

Step 4: Structure of the compound as per C 13   NMR

The peak shows three different types of hydrogen are present which are identical or symmetrical so the absorption is at the 132 due to vinyl carbon so the compound must be 3- hexene but the data does not distinguish between cis and trans.

 

The structure of the compound is 3-hexene

$C{H}_{3}C{H}_{2}CH=CHC{H}_{2}C{H}_3$