Unit Processes Multiple Choice Questions on “Hydrogenolysis Reactions”.
1. What is meant by Hydrogenolysis?
a) Addition of molecule
b) Cleavage of molecule
c) Unsaturated compound
d) All of the mentioned
Answer: b
Clarification: The term hydrogenolysis is a more exact expression than destructive of hydrogenation and refers particularly to cleavages in a molecule associated with the addition of hydrogen.
2. Hydrogenolysis is analogous to which reaction?
a) Hydrolysis
b) Alcoholysis
c) Ammonolysis
d) All of the mentioned
Answer: d
Clarification: Hydrogenolysis is analogous to the reactions commonly termed hydrolysis, alcoholysis, and ammonolysis which involve cleavage of a bond induced by the action of water, alcohol, or ammonia, respectively.
3. ‘ C-C’ linkage are cleaved by what in hydrogenation?
a) Catalyst
b) Nickel
c) Hydrogen
d) Zinc
Answer: b
Clarification: Carbon-Carbon Linkages. Such linkages are frequently cleaved by hydrogen in the presence of hydrogenation catalysts.
4. Cyclic hydrocarbons containing five- and six-membered rings do not undergo reaction.
a) True
b) False
Answer: a
Clarification: Cyclic hydrocarbons containing five- and six-membered rings are stable and do not undergo change except the usual degradative decompositions at higher temperatures.
5. Cresols yield aromatic hydrocarbons on hydrogenolysis over which catalyst?
a) Nickel
b) Zinc
c) Cadmium
d) All of the mentioned
Answer: a
Clarification: Phenol, polyphenols, and cresols yield aromatic hydrocarbons on hydrogenolysis over nickel catalysts at temperatures above 250°C.
6. Lactones undergo hydrogenolysis to give ether.
a) True
b) False
Answer: b
Clarification: Lactones undergo hydrogenolysis to give glycols, acids, or tetrahydrofurans.
7. Pyridine on hydrogenolysis produces what?
a) Hydrocarbon
b) Ammonia
c) Both hydrocarbon and ammonia
d) None of the mentioned
Answer: c
Clarification: Carbon-Nitrogen Linkages. Such linkages also cleave on hydrogenolysis. Thus, pyridine and pyrrole give ammonia and hydrocarbons.
8. What is meant by stepwise reduction?
a) Cleaving
b) Addition
c) Partial
d) All of the mentioned
Answer: c
Clarification: The term selectivity as recognized in catalytic hydrogenations refers either to the partial or stepwise reduction of a single molecule.
9. How is Selective hydrogenations accomplished?
a) Catalyst
b) Temperature
c) Pressure
d) All of the mentioned
Answer: d
Clarification: Selective hydrogenations are accomplished either by making the proper choice of catalyst, temperature, pressure, and solvent (and thereby attaining a difference in reaction rate) or by interrupting the reaction when the desired amount of hydrogen has been absorbed.
10. On increasing hydrogen pressure what happens to selectivity?
a) Increases
b) Decreases
c) Non change
d) All of the mentioned
Answer: b
Clarification: An increase of hydrogen pressure generally decreases selectively and an increase of temperature appears to increase it.
11. “Inactive” catalysts appear to be more useful than “active” ones.
a) True
b) False
Answer: a
Clarification: “Inactive” catalysts appear to be more useful than “active” ones and are obtained either by “poisoning” (adding mercury to palladium, for example) or by greatly diluting a catalyst with an inert carrier.