Topic: Alcohols Phenols and Ethers (Test 1)



Topic: Alcohols Phenols and Ethers
Q.1

Give IUPAC name of the compound given below.


A. 5 – Chlorohexan – 2 – ol
B. 2 – Hydroxy – 5 – chlorohexane
C. 2 – Chlorohexan – 5 – ol
D. 2 – Chloro – 5 – hydroxyhexane
Answer : Option A
Explaination / Solution:

-OH is given preference over -Cl so numbering is done so that –OH gets the lowest number.


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Q.2

A hydrocarbon C5H10 does not react with chlorine in dark but gives a single monochloro compound C5H9Cl in bright sunlight. The hydrocarbon is


A. Cyclopentane
B. Cyclopentene
C. Cycloalkyne
D. Cyclosporine
Answer : Option A
Explaination / Solution:

Cyclopentane is nearly inert chemically, they react with halogens in the presence of light through the substitution of one hydrogen atoms. Since the cyclic structure confers a high degree of symmetry on the molecule, only one monochloro cyclopentane is possible.


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Q.3
Phenol is less acidic than ______________.
A. o – nitrophenol
B. o – methylphenol
C. o – methoxyphenol
D. ethanol
Answer : Option A
Explaination / Solution:

The nitro-group is an electron-withdrawing group. The presence of this group in the ortho or para position decreases the electron density in the OH bond. As a result, it is easier to lose a proton. Also, the o-nitrophenoxide or p-nitrophenoxide ion formed after the loss of protons is stabilized by resonance. Hence, ortho and para nitrophenols are stronger acids than phenol.

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Q.4
Which of the following is most acidic?
A. Benzyl alcohol
B. Phenol
C. m – Chlorophenol
D. Cyclohexanol
Answer : Option C
Explaination / Solution:

In cases of halogen derivatives of phenols or aniline or benzoic acid etc, it is very helpful to understand that all halogens when attached to benzene ring exerts -I as well as +R effect. In case of Cl, Br and I, the +R effect has almost no effect on reactivity, acidic character or basic character of benzene ring. It is due to very less effective overlapping involving 2p of carbon and 3p or 4p or 5p of halogen. Hence, only -I effect becomes the deciding factor, which is most dominant from ortho-position and least effective from para-position. So m chlorophenol is most acidic.

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Q.5

Mark the correct order of decreasing acid strength of the following compounds.


A. e > d > c > b > a
B. b > d > c > a > e
C. e > d > b > a > c
D. d > e > c > b > a
Answer : Option B
Explaination / Solution:

B will be most acidic because of –M effect of NO​​​​​2 . Followed by d, in d –I effect of NO​​​​​2 operates only. Then c will come as –I of OCH​​​​3 < - I of NO​​​​​2  and least will be e because of +M effect of OCH​​​​3 that will decrease the acidity


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Q.6
Anisole can be prepared by the action of methyl iodide on sodium phenate. The reaction is called
A. Wurtzs reaction
B. Fittigs reaction
C. Etards reaction
D. Williamsons reaction
Answer : Option D
Explaination / Solution:

The reaction of alkyi halide with sodium alkoxide to give ether (alkoxy alkane), is known as Williamsons synthesis. In this reaction an ether (anisole) is prepared by the action of alkyi halide (methyl iodide) on sodium alkoxide (sodium phenate), so it is an example of Williamsons synthesis.


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Q.7
n – propyl bromide on treating with alcoholic KOH produces
A. propene
B. propane
C. propanol
D. propyne
Answer : Option A
Explaination / Solution:

Alkenes can be prepared from alkyl halides by treatment with alcoholic solution of caustic potash (KOH) at about 353-363 K. This reaction is known as dehydrohalogenation of alkyl halides.


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Q.8
Which of the following reactions will yield phenol?
A. ii,iii,iv
B. i,iii,iv
C. i, ii, iii
D. i,ii,iv
Answer : Option C
Explaination / Solution:

Preparation of phenols from haloarenes: Chlorobenzene is an example of haloarenes which is formed by mono substitution of benzene ring. When chlorobenzene is fused with sodium hydroxide at 623K and 320 atm sodium phenoxide is produced. Finally, sodium phenoxide on acidification gives phenols. Preparation of phenols from diazonium salts: When an aromatic primary amine is treated with nitrous (NaNO2 + HCl) acid at 273 – 278 K, diazonium salts are obtained. These diazonium salts are highly reactive in nature. Upon warming with water, these diazonium salts finally hydrolyse to phenols. Phenols can also be obtained from diazonium salts by treating it with dilute acids. Preparation of phenols from benzene sulphonic acid: Benzenesulphonic acid can be obtained from benzene by reacting it with oleum. Benzenesulphonic acid thus formed is treated with molten sodium hydroxide at high temperature which leads to the formation of sodium phenoxide. Finally, sodium phenoxide on acidification gives phenols.

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Q.9
Glycerol is
A. 1, 2, 3 – hydroxy propane
B. 1, 2, 3 – trihydroxy propane
C. Propane – 1, 2, 3 – triol
D. Propane – 1, 2, 3 – ol
Answer : Option C
Explaination / Solution:


Glycerol and trihydroxypropane are common names. The IUPAC name is propane-1,2,3-triol. The common name glycerol comes from the root glyco- which means sweet. Glucose, glycogen, and glycerin (another name for glycerol) have the same etymology.
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Q.10
Isopropyl alcohol on oxidation forms:
A. Acetaldehyde
B. Acetone
C. Methane
D. Ether
Answer : Option B
Explaination / Solution:

Secondary alcohols are oxidized to ketones. The oxidation of isopropyl alcohol by potassium dichromate (K2Cr2O7) gives acetone, the simplest ketone: Unlike aldehydes, ketones are relatively resistant to further oxidation, so no special precautions are required to isolate them as they form.

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