INTEC Chemistry Blog

CHM556 lab questions.

Posted on: March 30, 2013

CHM555 labs. Questions. Give brief but meaningful answer the questions.

Week 1. Experiment 1: Extraction of caffeine from a tea bag.

a) Caffieine acts as a base. What problem might occur if we did NOT add Na2CO3 to the boiled tea solution.
b) What part of the molecule is responsible for its basic behaviour
c) The % yield can vary. Give reasons why this may be.
d) Is DCM polar?
e) Propose an alternative solvent to DCM
f) What % of the tea bag was caffeine.
g) What errors/procedural steps may have decreased the yield of caffeine?
h) What may have caused an apparent increased the yield?
NEW:
Q1) What was the purpose of boiling the tea bag in water ?
Q2) Why not extract with just one large portion/volume of DCM instead of multiple small volumes of DCM>
Q3) Why use DCM instead of a different solvent like acetone?

Week 2. Experiment 2: Sodium Borohydride reduction of cyclohexanone.
Q1) What is the purpose of adding methanol to cyclohexanone?
Q2) Why was the mixture cooled after NaBH4 was added?
Q3) What was the gas observable as small bubbles after NaBH4 was added? and why was it produced?
Q4) Why was a test tube used instead of a separating funnel?
Q5) Comment on the yield of alcohol produced.

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