This set of Organic Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Preparation of Alcohols”.
1. Catalytic reduction (Hydrogenation) of carbon monooxide with H2 under high pressure and temperature gives methyl alcohol. What is this process is known as?
a) Baeyer’s test
b) Hofmann’s reaction
c) Kolb process
d) BASF process
Explanation: Currently, a Cu/ZnO/Al2O3 catalyst system has been employed industrially in MeOH synthesis for over half a century (a worldwide demand of 75 Mtons•year−1). It was run mostly at elevated pressures. (5–10 MPa) and high temperature (493–573 K) by feeding a CO (5%)-CO2 (5%)-H2 syngas stream.
2. Which of the following statements is incorrect regarding preparation of alcohols?
a) Aldehydes and Ketones on catalytic reduction by [H] give primary alcohol and secondary alcohol respectively
b) Ketones on reaction with Grignard’s reagent gives tertiary alcohol
c) Aldehydes on reaction with Grignard’s reagent gives primary or secondary alcohol
d) Alkyl halides on reaction alcoholic potash gives alcohol
Explanation: Whenever an alkyl halide reacts with alcoholic potash (or alcoholic sodium hydroxide), beta-elimination of the halide occurs, leading to the formation of an alkene.
3. Which of the following steps is not used in the fermentation of starch into ethyl alcohol?
a) Hydrolysis of starch into maltose by diastase present in barley
b) Conversion of maltose into glucose by maltase present in yeast
c) Conversion of glucose into ethanol by zymase present in yeast
d) Conversion of sucrose into glucose and fructose by sucrase present in yeast
Explanation: Conversion of sucrose into glucose and fructose by sucrase present in yeast steps is not used in the fermentation of starch into ethyl alcohol.
4. 15% pure ethyl alcohol (wash) on fractional distillation gives 95% ethyl alcohol by weight which is commonly known as which of the following terms?
b) Absolute alcohol
c) Rectified spirit
d) Methylated spirit
Explanation: Rectified spirit obtained from the distillation of the fermentation liquor wash contains about 95% of ethanol.
5. Ethyl alcohol obtained by fermentation of starch or molasses is called wash, and what is it’s purity?
Explanation: The alcohol obtained from molasses is called “wash” which contains the low percentage of ethyl alcohol (15-30%).
6. Which is the only alcohol that can be prepared by the indirect hydration of alkene?
a) Ethyl alcohol
b) Propyl alcohol
c) Isobutyl alcohol
d) Methyl alcohol
Explanation: Alkenes can be hydrated directly or indirectly which results in the formation of alcohols. First step is the reaction of alkene with sulphuric acid to give alkyl sulphate esters and second step is Direct hydration i.e. protonation of alkenesthen reaction with water to give alcohols.
7. Acid catalysed hydration of alkenes except ethene leads to the formation of which of the following?
a) Mixture of secondary and tertiary alcohols
b) Mixture of secondary and tertiary alcohols
c) Secondary or tertiary alcohol
d) Primary alcohol
Explanation: Acid catalysed hydration of alkenes except ethene leads to the formation of mixture of secondary and tertiary alcohols.
8. Among the alkenes which one produces tertiary butyl alcohol on acid hydration?
Explanation: When treated with aq. acid, most commonly H2SO4, alkenes form alcohols. Regioselectivity predicted by Markovnikov’s rule. Reaction proceeds via protonation to give the more stable carbocation intermediate. Not stereoselective since reactions proceeds via planar carbocation.
9. Which of the following way is not a method of preparation of alcohol?
a) Grignard reaction
b) Reduction of an aldehyde, ketone, or carboxylic acid with the appropriate reducing agent
c) Substitution reaction of hydroxide or water on the appropriate alkyl halide
d) Haber’s process
Explanation: Haber’s process is not a method for preparation of alcohol, ammonia is formed via this method.
10. Isopropyl methyl ether when treated with cold hydrogen iodide gives which of the following alcohol?
a) isopropyl iodide and methyl iodide
b) isopropyl alcohol and methyl iodide
c) isopropyl alcohol and methyl alcohol
d) isopropyl iodide and methyl alcohol
Explanation: When ethers are treated with strong acid in the presence of a nucleophile, they can be cleaved to give alcohols and alkyl halides. If the ether is on a primary carbon this may occur through an SN2 pathway.
Sanfoundry Global Education & Learning Series – Organic Chemistry.
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