Sindh Mdcat Exclusive Course Chemistry Alcohols Phenols And Ethers — Solved MCQs

Question 1

Which of the following compounds will give a secondary alcohol after reaction with NaBH4?

Accepted Answer

A. CH3COCH3 — Option A is a ketone, and its reduction (NaBH4 is a reducing agent) results in a secondary alcohol. This is because the carbonyl functional group is present in the middle of the chain so, the hydroxyl group is formed in the same place after reduction, giving a secondary alcohol. Option B is an ester, which does not undergo reduction with NaBH4.Option C is an aldehyde, that forms a primary alcohol, upon reduction, as its carbonyl group is towards the terminal end of the chain, thereby forming a terminal hydroxyl group. Option D is a carboxylic acid, which does not undergo reduction with NaBH4.

Question 2

The test used to distinguish among primary, secondary, and tertiary alcohols is:

Accepted Answer

C. Lucas Test — Lucas' Solution is a solution of anhydrous ZnCl and concentrated HCl and we use this solution to examine the class of alcohol that we are dealing with. The difference is present between the time taken for the alcohol to convert into chloroalkane. This change is marked by the solution becoming milky white from colourless and also an oily layer is formed on the surface of the solution during the reaction by the chloroalkane formed. Tertiary alcohols show the results almost immediately, followed by secondary alcohols showing results between 3-5 minutes. The primary alcohols do not show a result unless heated. 2,4 - DNPH is a test for the detection of aldehydes and ketones. Tollens and Fehling Solution are used to differentiate between an aldehyde and ketone. Only Aldehydes gives Tollens and Fehlings tests.

Question 3

Primary Alcohol is produced by reactions of Grignard's reagent with _ followed by hydrolysis in an acidic medium.

Accepted Answer

B. Formaldehyde — The Grignard Reaction is the addition of an organomagnesium halide (Grignard reagent) to a ketone or aldehyde, to form tertiary or secondary alcohol, respectively. The reaction with formaldehyde leads to primary alcohol.

Question 4

Ethanol, when reacted with PCI5 , gave A, POCl3, and HCI. A reacts with AgNO2 to form B and AgCl. A and B are respectively:

Accepted Answer

C. C2H5Cl and C2H5NO2 — C2H5Cl and C2H5NO2 are the products of the following reaction equation: C2H5OH + PCl5 -----> C2H5Cl + POCl3 + HCl C2H5Cl + AgNO2 -----> C2H5NO2 + AgCl

Question 5

Which of the following is not a physical property of ethers?

Accepted Answer

D. It is poisonous and is used as a disinfectant in hospitals — Ethers are typically volatile liquids that show weak hydrogen bonding. They are also highly flammable and have low boiling points, which makes them useful as solvents. Ethers are not poisonous and are not used as disinfectants in hospitals.

Question 6

By fermentation process of starch and by the catalytic enzyme, _ is produced.

Accepted Answer

B. Ethyl alcohol — Starch essentially breaks down to give glucose which undergoes the process of glycolysis to give pyruvate and NADH alongside ATP. Pyruvate undergoes decarboxylation to give ethanal and ethanal is reduced by NADH to give ethanol which is an ethyl alcohol. This is, basically, the summarization of the alcohol fermentation so the answer is B.

Question 7

The product formed by acid catalysed hydration of 2 - phenyl propene is:

Accepted Answer

B. 2 - phenyl - 2 - propanol — The answer is B as we have the phenyl on the second carbon and the double bond being either between carbon number 1 and 2 or between carbon number 2 and 3. Based on the information about the position of the phenyl group, we can rule out options A, C, and D as all three show the phenyl having its position changed which is not possible. Hydration would remove the double bond, replacing it with a hydroxyl group that could be on either three of the carbons. As we only have option B satisfying our condition of the phenyl group being on the second carbon, we can infer the hydroxyl is on the second carbon as well based on the options provided. Also remember, the major product obtained on acid - catalysed hydration of 2-phenylpropene is 2-Phenylpropan-2-ol.

Question 8

The compound ‘leaf alcohol’ is partly responsible for the smell of new - mown grass CH3CH2CH=CHCH2CH2OH Leaf alcohol Which two compounds will be formed when ‘leaf alcohol’ is oxidized using hot, concentrated manganate (VII) ions?

Accepted Answer

C. CH3CH2CO2H and HO2CCH2CO2H — The answer is C as when the double bond breaks, based on the structure of both the carbons involved in the double bond, each having a hydrogen attached alongside an organic chain, aldehydes would be formed. Both the aldehydes would be oxidized to give carboxylic acid. CH3CH2COOH is formed plus COOHCH2CH2OH with the latter being a primary alcohol. It would be further oxidized to give a dicarboxylic acid which is HOOCCH2COOH, thus the answer is C.

Question 9

Rectified spirits have a percentage of alcohol.

Accepted Answer

C. 95 % — Option A: 12% alcohol is the typical alcohol content of beer. Option B: 24% alcohol is the typical alcohol content of wine. Option C: Rectified spirit has a percentage of alcohol of 95%. It is a type of ethanol that has been purified through a process called rectification. Rectification is a distillation process that separates ethanol from water. The ethanol is then concentrated to a high level of purity. Rectified spirit is often used as a solvent in industrial applications. It is also used in the production of alcoholic beverages, such as vodka and gin. However, it is not safe to drink rectified spirit because it can be toxic. Option D: 100% alcohol is pure ethanol.

Question 10

Which of the following alcohol does not get oxidized when it reacts with K₂Cr₂O₇/H₂SO₄?

Accepted Answer

A. CH₃C(CH₃)₂OH — Option A is a tertiary alcohol which cannot be oxidized with K2Cr2O7 as the central carbon atom has no free hydrogens. Option B is a secondary alcohol which oxidizes to a ketone. Option C is methanol which oxidizes to carbondioxide. Option D is ethanol which oxidizes to ethanal first then ethanoic acid.

Question 11

The alkenes can be formed by alcohols in the presence of

Accepted Answer

D. pyridine — Alcohols react with pyridine in POCl3 to form alkenes.

Question 12

In the Lucas test, tertiary alcohols form an oily layer of alkyl halide _.

Accepted Answer

B. Immediately — Option A: On heating is incorrect because heating is not required for the reaction to take place. The reaction occurs at room temperature. Option B: The Lucas test in alcohols is a test to differentiate between primary, secondary, and tertiary alcohols. Tertiary alcohols react immediately with the Lucas reagent as evidenced by turbidity owing to the low solubility of the organic chloride in the aqueous mixture. Option C: After 5-10 minutes is also incorrect because the reaction is very fast and occurs immediately. The turbidity or precipitation of the solution is typically observed within a few seconds to a minute after the addition of the Lucas reagent. Option D: After 20 minutes is also incorrect because the reaction is very fast and occurs immediately. The turbidity or precipitation of the solution is typically observed within a few seconds to a minute after the addition of the Lucas reagent.

Question 13

Why is phenol more acidic than Alcohol?

Accepted Answer

C. Both Options A and B are correct — Phenol is more acidic than alcohol due to the stabilization of the phenoxide ion through resonance. The presence of an electron-withdrawing group increases the acidity of phenol by stabilizing the phenoxide ion.

Question 14

Glycerol can also be termed as?

Accepted Answer

B. 1, 2, 3 - propanetriol — Glycerol contains three carbons, giving it the “propane” part to its name. It has an OH group attached to each carbon which account for “1,2,3- triol” Hence, option B is correct as it has 3 hydroxyl groups.

Question 15

What is the other name of 2,4,6-trinitrophenol?

Accepted Answer

A. Picric acid — Correct option is A. The other name of 2,4,6-trinitrophenol is picric acid. It is a yellow, crystalline solid that is highly explosive. It is also a strong acid and can cause severe burns. The name "picric" comes from the Greek word "pikros", which means "bitter". This is because picric acid has a very bitter taste. Picric acid was first synthesized in 1771 by Carl Wilhelm Scheele. It was originally used as a yellow dye, but it was later found to be too explosive for this purpose. Today, picric acid is used mainly as an explosive. It is also used in some fireworks and as a component of some smokeless powders.

Question 16

Which one of the following shows that iodoform test for a compound is positive?

Accepted Answer

C. Yellow crystals — Explanation for this question will be added soon.

Question 17

Which of the following is an insecticide?

Accepted Answer

A. DDT — DDT or dichlorodiphenyltrichloroethane is a colorless crystalline compound commonly used as an insecticide in the agriculture sector. It works by ceasing the nervous function in insects.

Question 18

This is used as substrate during formation of alcohol:

Accepted Answer

B. Glucose — Alochol is prepare from fermentatiom of molasses and starch which are converted to glucose to prepare ethanol. is used as a substrate in the formation of alcohol through the process of biological fermentation.

Question 19

Phenol is also called _.

Accepted Answer

B. Carbolic acid — Option A: Carbonic acid is a carbon-containing compound which has the chemical formula H2CO3. Solutions of carbon dioxide in water contain small amounts of this compound.Option B: Phenol is an aromatic compound. The chemical formula of this organic compound is C6H6O. Phenol is also known as Carbolic acid. It consists of a hydroxyl group and a phenyl group attached to each other.Option C: Acetic acid is also known as ethanoic acid, ethylic acid, vinegar acid, and methane carboxylic acid; it has the chemical formula of CH3COOH. Acetic acid is a byproduct of fermentation, and gives vinegar its characteristic odor.Option D: Hydroxy acids, also known as polycarboxylic acids, has two carboxylic groups, at least. They can also present one carboxylic group or a hydroxyl group with a ketone. The most common hydroxy acids used to make multicomponent complexes with cyclodextrin are: citric acid, tartaric acid, glycolic acid, oxalic acid.

Question 20

Which of the following catalyst is used in the industrial preparation of methanol?

Accepted Answer

D. Zinc oxide and Chromium oxide — The industrial preparation of methanol usually involves a catalyst composed of zinc oxide and chromium oxide. This catalyst is known as a copper-zinc-chromium catalyst, and it is commonly used in the synthesis of methanol from a mixture of carbon monoxide and hydrogen gases in a process known as the "methanol synthesis gas." This catalytic process is known as the "low-pressure methanol synthesis" and is widely used in industry.

Sindh Mdcat Exclusive Course Chemistry Alcohols Phenols And Ethers — Solved Past Paper with Answers

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