Practice Quiz - Hydration of an Alkyne

(1) When the aqueous reaction mixture is placed in a separatory funnel and extracted with methylene chloride, which layer will be on top?

(a) aqueous

(b) methylene chloride

(d) neither: they are immiscible

(2) The reaction period is over, the extraction has been performed, and you have placed the organic layer containing product and solvent in a round bottom flask and begun a distillation. What do you expect to be the first compound distilling?

(a) methylene chloride

(b) unreacted starting material

(d) water

(3) What is the purpose of the H₂SO₄ in the hydration of 2-methyl-3-butyn-2-ol using HgO?

(a) to protonate the -OH group on 3-hydroxy-3-methyl-2-butanone

(b) to neutralize the HgO

(d) to form the catalyst, Hg+2, from HgO

(4) The hydration of an alkyne experiment that you do is an example of anti-Markovnikow addition.

(a) true

(b) false

(5) In the hydration of terminal alkynes, more than one hydration product can form.

(a) true

(b) false

(6) Draw the keto tautomer of the following enol:

(7) Give all the products of the following reaction:

The balanced reaction for the hydration of an alkyne is:

compound MW bp mp density misc.

2-methyl-3-butyn-2-ol 84 104 3 0.86

3-hydroxy-3-methyl-2-butanone 102 140 .......... 0.97

H₂SO₄ (conc.) 98 ...... ....... 1.84 conc. H₂SO₄ is 18M

methylene chloride 85 40 -95 1.33

mercuric oxide, HgO 217 .......... 500 1.1

(8) You begin with 0.2 g HgO, 17 mL water, 3.3 mL H₂SO₄, and 5 mL of the alkyne. What is the limiting reagent?

(a) HgO

(b) water

(d) alkyne

Answers.

compound	MW	bp	mp	density	misc.
2-methyl-3-butyn-2-ol	84	104	3	0.86
3-hydroxy-3-methyl-2-butanone	102	140	..........	0.97
H₂SO₄ (conc.)	98	......	.......	1.84	conc. H₂SO₄ is 18M
methylene chloride	85	40	-95	1.33
mercuric oxide, HgO	217	..........	500	1.1