Discussion
The number of chemically non-equivalent protons expected in 1H-NMR spectrum of 2-pinene is :
![Structure of 2-pinene (alpha-pinene): a bicyclo[3.1.1]heptene with a methyl on the double bond and a gem-dimethyl bridge](/uploads/question-images/sppu-mhset-2019-06-23-chemical-sciences-paper-2/q49.png)
Answer: B
2-Pinene (α-pinene) shows 10 kinds of non-equivalent protons.
Count the environments in this chiral, unsymmetrical bicyclic alkene:
- the vinyl H on C-3: 1
- the methyl on the double bond: 1
- the two methyls of the gem-dimethyl bridge, one syn and one anti to the double bond: 2
- the bridgehead H on C-1 and the bridgehead H on C-5: 2
- the two diastereotopic H on the allylic CH2 (C-4): 2
- the two diastereotopic H on the CH2 bridge (C-7): 2
That totals 10. Answers of 7 or 6 come from treating the gem-dimethyls or the CH2 protons as equivalent, which they are not in this rigid ring system.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development