12th Standard Chemistry English Medium Hydroxy compounds and ethers Reduced Syllabus Important Questions 2021

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Questions:

Multiple Choice Question

15 x 1 = 15

The IUPAC name of phenetole is _______.

(a)

ethoxybenzene

(b)

methyl phenyl ether

(c)

diethyl ether

(d)

diphenyl ether

Ethers are functional isomers of ________.

(a)

acids

(b)

alcohols

(c)

nitro compounds

(d)

aldehydes

C₆H₅ - O - CH₃ is an example of ________.

(a)

nitriles

(b)

mixed ether

(c)

symmetrical ether

(d)

anhydride

Ether is formed when alkylhalide is treated with sodium alkoxide, this method is known as ________.

(a)

Hoffmann reaction

(b)

Williamson's synthesis

(c)

Wurtz synthesis

(d)

Kolbe's reaction

Intermolecular hydrogen bonds are not _______ present in.

(a)

CH₃COOH

(b)

C₂H₅OC₂H₅

(c)

CH₃CH₂OH

(d)

C₂H₅NH₂

When phenol reacts with CCl₄and NaOH, the product formed is ________ acid.

(a)

salicylic

(b)

cinnamic

(c)

benzoic

(d)

carboxylic

Lucas reagent is _______.

(a)

ZnCl₂

(b)

cone. H₂SO₄ and anhydrous ZnSO₄

(c)

ZnSO₄

(d)

cone. HCl and anhydrous ZnCl₂

The structure of cumene is ________.

(a)

(b)

(c)

(d)

None

The IUPAC name for isobutyl alcohol is _______.

(a)

2-methyl-l-propanol

(b)

2-methyl-l-butanol

(c)

2,2-dimethyl-2-propanol

(d)

1,1-dimethyl- 2-butanol

10.

When alcohols are converted to alkyl chlorides by thionyl chloride in presence of pyridine the intermediate formed is ______.

(a)

sulphonium ion

(b)

chlorosulphonic acid

(c)

alkyl chlorosulphite

(d)

chlorosulphite

11.

Ethers in the presence of atmospheric oxygen oxidises to give hydroperoxides and dialkyl peroxides Such a spontaneous reaction by atmospheric oxygen is called ______.

(a)

auto oxidation

(b)

acylation

(c)

alkylation

(d)

dehydration

12.

Compound of molecular formula C₇H₈O is a sweet smeeling liquid. A on reaction with acidified K₂Cr₂O₇ gives compound B of molecular formula C₇H₈O. B reduces Tollen's reagent A and B are respectively.

(a)

benzaldelyde and benzoic acid

(b)

Methyl phenykarbinol and acetophenone

(c)

benzyl alcohol and benzaldehyde

(d)

diphenyl carbinol and benzophenone

13.

Higher alcohols are not soluble in water because of ______.

(a)

hydrophilic alkyl group

(b)

hydrophobic alkyl groups

(c)

hydrophilic aryl group

(d)

hydrophobic aryl groups

14.

Among the following ethers which one will produce methyl alcohol on treatment with hot HI?

(a)

(H₃C)₃C-O-CH₃

(b)

(CH₃-)₂-CH-CH₂-O-CH₃

(c)

CH₃-(CH₂)₃-O-CH₃

(d)

CH₃-CH₂-\(\underset { \overset { | }{ { CH }_{ 3 } } }{ CH } \)-O-CH₃

15.

The reaction

Can be classified as ______.

(a)

dehydration

(b)

Williams on alcoholsynthesis

(c)

Williamson ether synthesis

(d)

dehydrogenation of alcohol

Generic 3

14 x 3 = 42

16.

Halo alkane are easily prepared from alcohols while alkyl halides cannot be prepared from phenol. Justify.

17.

When tertiary butyl alcohol and 1-butanol are separately treated with a few drops of KMnO₄, in one case only the purple colour disappears and a brown precipitate is formed. Which of the two alcohols gives the above reaction and what is that brown precipitate?

18.

How do ethers react with HI? Give the significances of the reaction.

19.

Ethers should not be heated to dryness. Why?

20.

How can the following conversion be effected? (i) Phenol to phenolphthalein.

21.

Give the IUPAC names of each of the following and classify them as 1°, 2° and 3°
(a) CH₃(CH₂)₃CHOHCH(CH₃)₂
(b) (CH₃)₃C-CH₂OH
(c) \(({ CH }_{ 3 })_{ 2 }\underset { \overset { | }{ { C }_{ 6 }{ H }_{ 5 } } }{ C } -OH\)
(d) \(BrCH_{ 2 }-\underset { \overset { | }{ OH } }{ { CH }_{ 2 } } -CH-C({ CH }_{ 3 })_{ 3 }\)
(e) CH₂=CH-CHOHCH
(f) PhCH₂OH
(g) HOCH₂CH₂CH₂CH₂C₆H₅
(h) (C₂H₅)₃COH

22.

Account for the following:
(a) Lower members of alcohols are soluble in water but higher members are not.
(b) Alcohols cannot be used as solvent for Grignard reagent.

23.

When phenol on treatement with Br₂/H₂O readily gives a precipitate of 2, 4, 6 - tribomo phenol.

24.

Phenol is distilled with Zn dust followed by friedel – crafts alkylation with prophyl chloride to give a compound B, B on oxidation gives (c) Indentify A,B and C.

25.

How is phenol prepared from
i) chloro benzene
ii) isopropyl benzene

26.

What happens when 1-phenyl ethanol is treated with acidified KMnO₄.

27.

Is it possible to oxidise t – butyl alcohol using acidified dichromate to form a carbonyl compound.

28.

Predict the major product, when 2-methyl but -2-ene is converted into an alcohol in each of the following methods.
(i) Acid catalysed hydration
(ii) Hydroboration
(iii) Hydroxylation using Baeyer's reagent

29.

Draw the major product formed when 1-ethoxyprop-1-ene is heated with one equivalent of HI.

Generic 2

7 x 2 = 14

30.

How can isopropyl alcohols be converted to t-butyl alcohol?

31.

Preparation of ethers by intermolecular dehydration of alcohols in the presence of an add is not a suitable method for mixed ethers. Give reason.

32.

Give a test to identify whether a given -OH group is alcoholic or phenolic in nature.

33.

Write the IUPAC names of
(a) C₂H₅OCH₃
(b) C₆H₅OC₂H₅

34.

Why sodium metal cannot be used to dry alcohols but it can be used to dry ethers?

35.

Give the IUPAC names of
(i) CH₃CH(OH)CH₂OH
(ii) HO-CH₂-CH₂-OH
(iii) \({ { CH } }_{ 3 }-\underset { \overset { | }{ OH } }{ CH } -COOH\)

36.

Explain why phenol does not undergo substitution of the -OH group like alcohol.

Generic 5

6 x 5 = 30

37.

An organic compound 'A' is a sodium salt of phenolic acid with molecular formula C₇H₅O₃Na. 'A' on heating with soda lime gives compound 'B' of molecular formula C₆H₆O. 'B' gives violet colour with neutral ferric chloride. 'B' on treatment with C₆H₅COCI in the presence of NaOH gives an ester 'C'. Identify 'A', 'B' and 'C'. Explain the reactions.

38.

What are ethers? Write note on simple and mixed ethers with examples.

39.

How would you distinguish between (i) methyl alcohol and ethyl alcohol (ii) benzyl alcohol and phenol, (iii) ethyl alcohol and benzyl alcohol?

40.

How will you distinguish the primary, secondary and tertiary alcohols by Victor Meyer's method?

41.

Explain the mechanism involved in the intermolecular dehydration of alcohols to give ethers.

42.

An organic compound A of molecular f formula C₆H₆O gives violet colouration with neutral FeCl₃. Compound A on treatment with metallic Na gives compound B. Compound B on treatment with CO₂ at 400 K under pressure gives C. This product on acidification gives compound D (C₇H₆O₃) which is used in medicine. Identify (A) (B) (C) and D and explain the reactions.

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Answers Key:

Multiple Choice Question

15 x 1 = 15

(a)
ethoxybenzene

(b)
alcohols

(b)
mixed ether

(b)
Williamson's synthesis

(b)
C₂H₅OC₂H₅

(a)
salicylic

(d)
cone. HCl and anhydrous ZnCl₂

(a)
2-methyl-l-propanol

10.

11.

(a)
auto oxidation

12.

13.

(b)
hydrophobic alkyl groups

14.

15.

Cyclic alcolhol → sodium cyclic alkoxide- Williamson ether synthesis.

Generic 3

14 x 3 = 42

16.

(i) Alcohols are weakly basic in nature so easily in presence of strong acids.
(ii) Due to the presence of +ve charge on the oxygen atom, C-O in protonated alcohols became weak hence easily cleaved by halide ions to form alkyl halides.
(iii) Where as phenols are much weaker bases due to delocalisation of the lone pair of electrons on the oxygen atom due to resonance and so are not easily protonated.
(iv) The C-O bond in phenols has some double bond character; hence not easily cleaved by halide ions to form respective alkyl halides.

17.

1-Butanol, being primary alcohol gets oxidised by dilute KMnO₄. The brown precipitate is due to the formation of manganese dioxide.

18.

Ethers can undergo nucleophilic substitution reactions with HBr or HI. HI is more reactive I than HBr.

19.

When ethers are heated to dryness,
(i) They form peroxide by the action of air or oxygen.
(ii) Ether oxygen is capable of forming a co-ordinate covalent bond with electron deficient species.

(ii) These peroxides are unstable and decomposes violently with explosion on heating. Hence, ether should not be heated to dryness.

20.

On heating phenol with phthalic anhydride in presence of con.H₂SO₄ phenolphthalein is obtained.

21.

(a) 2-methyl-heptan-3-ol (2°)
(b) 2,2-dimethyl-propan-1-01-(1°)
(c) 2-phenyl-2-propanol (3°)
(d) 2,2-dimethyl-S-bromo-3-pentanol (2°)
(e) l-Butene-ol (2°)
(f) Phenyl methanol (1°)
(g) 4-phenyl-1-butanol (1°)
(h) 3-ethyl-3-pentanol (3°)

22.

(a) Alcohols are soluble in water because they form intermolecular hydrogen bonding with water. Lower members are completely miscible with water and the higher members are not. This is because of the increase in size of hydrophobic (water repelling) alkyl group in the alcohol.
(b) Strong basic substances like organo metallic compounds (RMgX-Grignard reagent) are decomposed by alcohol.
R - OH + CH₃MgBr ⟶ R - O - Mg - Br + CH₄
Hence, alcohols cannot be used as a solvent for Grignard reagent.

23.

(i) Phenol reacts with bromine water to give a white precipitate of 2,4,6-tri bromo phenol.

(ii) It readily forms tribromo derivative since it has two-o and one-p position free with respect to OH group.

24.

\(\underset {Phenol} {\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}}+\mathrm{Zn}(\text { dust }) \rightarrow \underset {benzene(A)} {\mathrm{C}_{6} \mathrm{H}_{6}}+\mathrm{ZnO}\)

25.

(i) Chloro benzene:
When Chlorobenzene is hydrolysed with 6-8% NaOH at 300 bar and 633K in a closed vessel, sodium phenoxide is formed which on treatment with dilute HCl gives phenol.

(ii) isopropyl benzene:
A mixture of benzene and propene is heated at 523K in a closed vessel in presence of H₃PO₄ catalyst gives cumene (isopropylbenzene). On passing air to a mixture of cumene and 5% aqueous sodium carbonate solution, cumene hydro peroxide is formed by oxidation. It is treated with dilute acid to get phenol and acetone. Acetone is also an important byproduct in this reaction.

26.

27.

Tertiary alcohols do not undergo oxidation reaction under normal conditions, but at elevated temperature under strong oxidizing, agent cleavage of C-C-bond takes place to give a mixture of carboxylic acid.

28.

(i) Acid catalysed hydration

(ii) Hydroboration

(iii) Hydroxylation using Baeyer's reagent

29.

Generic 2

7 x 2 = 14

30.

31.

This method is useful for the preparation of simple ethers and not suitable for preparing mixed ethers. If a mixture of two different alcohols is used, mixture of different ethers will be formed and they are difficult to separate.

32.

Phenolic OR group gives a violet colouration with neutral FeCl₃ but alcoholic OR does not.

33.

Formula	IUPAC Name
(a) C₂H₅OCH₃	Methoxy ethane
(b) C₆H₅OC₂H₅	Ethoxy benzene

34.

Alcohols are acidic enough to react with sodium but ethers are inert.

35.

(i) Propane-1, 2-diol
(ii) Ethane-1,2 - diol
(iii) 2-Hydroxy propanoic acid

36.

In phenol the electron density is increased in the benzene ring and hence the benzene ring is activated towards electrophilic substitution reaction and -OH group does not undergo substitution reaction like alcohol.

Generic 5

6 x 5 = 30

37.

(i) The organic compound (A) which is sodium salt of phenolic acid is sodium salicylate.
(ii) (A) on heating with soda lime gives Compound (B) phenol. Phenol gives violet colouration with neutral perchloride.

(iii) Phenol on treatment with C₆H₅COCl in the presence of NaOH gives on ester 'C':
C₆H₅OH + C₆H₅COCl \(\overset { NaOH }{ \longrightarrow } \underset { (C) }{ { C }_{ 6 }{ H }_{ 5 }OCO{ C }_{ 6 }{ H }_{ 5 }+HCl } \)

Compound	Compound Name	Formula
A	Sodium benzoate'
B	Phenol	C₆H₅OH
C	Phenyl benzoate	C₆H₅OCO C₆H₅

38.

Ethers are a class of organic compound in which an oxygen atom is connected to two alkyl/aryl groups Ethers can be considered as the derivatives of hydrocarbon in which one hydrogen atom is replaced by an alkoxy (-OR) or an aryloxy (-OAr ) group. The general formula of aliphatic ether is C_nH_2n+2O.
Classification:

39.

(i) Methyl alcohol and Ethyl alcohol

S.No	Methyl alcohol	Ethyl alcohol
1.	It does not react with cone. H₂SO₄ at any temperature.	It reacts with cone. H₂SO₄ at 410K, to produces diethyl ether and at 440K it produces ethylene products.
2.	It does not react with I₂ + NaOH to form iodoform.	It reacts with I₂ + NaOH to produce iodoform CHI₃.

(ii) Benzyl alcohol and phenol

S.No	Benzyl alcohol	Phenol
1.	It does not give violet colour with neutral ferric chloride.	It gives-violet colour with neutral ferric chloride
2.	It does not decolourise bromin water.	It decolourise bromine water and produce 2,4,6- tribromo phenol.

(iii) Ethyl alcohol and benzyl alcohol

S.No	Ethyl alcohol	Benzyl alcohol
1.	It reacts with I₂ + NaOH to give iodoform	It does not react with I₂ + NaOH
2.	It does not undergo electrophilic substitution	It undergoes electrophilic substitution reactions at ortho and para positions.

40.

Victor Meyer's test:
This test is used to distinguish 1°, 2°, and 3° alcohols.
This test consists of the following steps:
(i) Alcohol is converted into alkyl iodide by treatment with P/I₂.
(ii) The alkyl iodide is then converted into nitro alkane by silver nitrate (AgNO₂).
(iii) The nitro alkane is treated with nitrous acid (HNO₂) and then with aqueous KOH.
(iv) The 1°,2° and 3° alcohols are identified from the colour of the product.

41.

Inter molecular dehydration of alcohol: We have already learnt that when ethanol is treated with con.HSO₂ 4 at 443K, elimination takes place to form ethene. If the same reaction is carried out at 413K, substitution competes over elimination to form ethers.

42.

(i) Compound A is phenol. (C₆H₅OH)
Phenols on reaction with metallic Na compound (B) ie., Sodium Phenoxide
\(\underset { (A) }{ { 3C }_{ 6 }{ H }_{ 5 }OH+2Na } \longrightarrow \underset { (B) }{ { 2C }_{ 6 }{ H }_{ 5 }ONa+{ H }_{ 2 } } \)
(ii) (B) is heated with CO₂ at 400K under pressure, to give (C). This is decomposed by dil.HCl, and (D) is formed