Before You Begin
Question #44477
The Question
Compound , \ce{1-(but-2-yn-1-yl)-4-isopropylbenzene}, is treated with a large excess of sodium metal in liquid ammonia containing ethanol at until complete reduction of all reducible functional groups occurs. The reaction yields as the major organic product. Which of the following represents the correct IUPAC name and stereochemistry of ?
Options
- A.
3-((E)-but-2-en-1-yl)-6-isopropylcyclohexa-1,4-diene
- B.
1-((E)-but-2-en-1-yl)-4-isopropylcyclohexa-1,4-diene
- C.
1-((Z)-but-2-en-1-yl)-4-isopropylcyclohexa-1,4-diene
- D.
3-((Z)-but-2-en-1-yl)-6-isopropylcyclohexa-1,4-diene
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Mechanism_Trap
Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.
Concepts Behind This Question
Lindlar vs. Birch Reduction|Hyperconjugation Logic|Reaction Intermediates Stability
Why This Question Is Tricky
Common Mistakes
Students overlook the steric override of electronic effects in the Birch reduction of bulky alkylbenzenes.
While standard rules dictate that EDGs (like alkyls) stabilize the double bonds and end up on carbons (1,4-dialkylcyclohexa-1,4-diene), bulky groups like isopropyl suffer severe allylic strain in this geometry.
This forces protonation at the electronically destabilized ipso-carbons, yielding the anomalous 3,6-dialkylcyclohexa-1,4-diene.
The inclusion of the alkyne tests the simultaneous application of standard stereoselective Birch reduction (yielding trans-alkenes) against this anomalous aromatic regioselectivity.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Hydrocarbons - Class 11 Part 2 |
| Concept | Lindlar vs. Birch Reduction |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |