MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Alcohols, Phenols and EthersNumerical
A student gets four alcohols labelled A to D: A is 2-methylpropan-2-ol, B is butan-2-ol, C is…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student gets four alcohols labelled A to D: A is 2-methylpropan-2-ol, B is butan-2-ol, C is butan-1-ol and D is 2-methylbutan-2-ol. She shakes each with the Lucas reagent at room temperature and watches for 10 minutes. Find how many of the four give a cloudy mixture at once, how many stay clear for the whole time, and how many give a cloudy mixture after about five minutes.
Need a reminder? The key ideaShow
Lucas test: tertiary at once, secondary in about five minutes, primary clear at room temperature. Dehydration follows Saytzeff's rule. Esterification is an equilibrium with . Primary alcohols oxidise to aldehydes and acids, secondary alcohols to ketones, and tertiary alcohols are not oxidised.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Four alcohols.
Step 1. Classes. A has three carbon neighbours on the OH carbon: tertiary. B has two: secondary. C has one: primary. D has three: tertiary.
Step 2. Lucas results. Tertiary alcohols give a cloudy mixture at once: A and D, so 2. The secondary alcohol B gives it after about five minutes: 1. The primary alcohol C stays clear: 1.
Check. , so every alcohol is placed.
Answer: 2 at once, 1 clear and 1 after about five minutes.
Discussion (0)
Log in to join the discussion.
Loading…