Question

Identify the expected base peak in the mass spectrum of 2,2,3-trimethylbutane. Draw the fragment associated with this peak and explain why the base peak results from this fragment.

Answer 1

Answer:

The base peak of the 2,2,3-trimethylbutane mass spectrum is the carbocation of (CH₃)₃C⁺, M⁺ = 57

Explanation:

Normally, the base peak is the most stable ion fragment after electron ionization. In our structure, the most stable fragment is the 'tert-butyl' ion, since it is a tertiary carbocation. The secondary peak which can also be observed is the 'isopropyl' ion.

(CH₃)₃C-CH(CH₃)₂ → (CH₃)₃C⁺ (M=57) , (CH₃)₂CH⁺ (M=43)

Attachment is the fragmentation of 2,2,3-trimethylbutane and mass of each fragment.