An alkyl tosylate Multiple Choice 2 points A dihalide in which the halogens [Free] A9
An alkyl tosylate Multiple Choice 2 points A dihalide in which the halogens are attached on adjacent carbons is called a dihalide Vicinal Geminal Vinylic Allylic Cis Multiple Choice 2 points Determine which compound will react with sodium in liquid ammonia to form trans – 3 – hexene. cis – 3 – hexene
Answer
🧪 Identification of Dihalide Type
A dihalide where the two halogen atoms are attached to adjacent carbon atoms is referred to as a vicinal dihalide. In contrast, if both halogens are attached to the same carbon, the compound is termed geminal (from Latin “geminus” meaning “twin”).
Other descriptors like vinylic, allylic, or cis describe different types of unsaturation or molecular arrangement and do not apply here.
✅ Correct Answer: Vicinal
⚙️ Formation of trans-3-hexene Using Sodium in Liquid Ammonia
The reduction of a vicinal dihalide using sodium (Na) in liquid ammonia (NH3) is a classic example of a dissolving-metal reduction. This reaction mechanism involves initial conversion of the dihalide into a radical intermediate, followed by anti elimination, which results in the formation of an alkene.
🔬 Mechanistic Insight:
- The halide groups on the adjacent carbon atoms must be positioned cis (on the same side).
- Anti elimination occurs during the reaction, forcing the remaining groups to adopt a trans configuration.
- This results in the production of trans-3-hexene, an alkene with a double bond between carbon 3 and 4 in the trans arrangement.
✅ Correct Answer: The cis-configured vicinal dihalide (cis-3,4-dibromohexane)
This specific molecular geometry is essential to obtain the desired trans stereochemistry of the final alkene via anti elimination facilitated by sodium in liquid ammonia.
📌 Summary of Answers
- Q1: Dihalide with halogens on adjacent carbons — Vicinal
- Q2: Compound yielding trans-3-hexene in Na/NH3 — Cis-configured vicinal dihalide (cis-3,4-dibromohexane)