Question

Question:Primary (1°) alcohols often show a peak in their mass spectra at m/z= 31. Suggest a structure for this fragment.

Short answer

Answer

Structure of the fragment that shows peak at m/z = 31

Step-by-step solution

α cleavage of alcohols

Alcohols undergo fragmentation to give a dehydrated radical cation and cations and neutral radicals uponα cleavage.

Step 2: α cleavage of primary alcohols

Primary alcohols can cleave to form an alkyl radical and a carbocation containing the alcohol group. This carbocation is resonance stabilized and has an m/z value of 31.

The cleavage of a primary alcohol is shown below:

αcleavageof primary alcohol

The cation formed is resonance stabilized; the canonical structure is shown below:

Resonance stabilization of the carbocation formed