CH 7:-

1. On reacting with grignard reagent acetone gives?

(A) 10alcohol (B) 20alcohol
(C) 30alcohol (D) None of these

c. 30alcohol
Explanation:

2. Arrange the following compounds in increasing order of boiling point.

Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol.
(A) Propan-1-ol, butan-2-ol, butan-1-ol, pentan-1-ol.
(B) Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol.
(C) Pentan-1-ol, butan-2-ol, butan-1-ol, propan-1-ol.
(D) Pentan-1-ol, butan-1-ol, butan-2-ol, propan-1-ol.

a. Propan-1-ol, butan-2-ol, butan-1-ol, pentan-1-ol

Explanation:
The boiling points of alcohols and phenols increase with increase in the number of
carbon atoms (increase in van der Waals forces.). In alcohols, the boiling points
decrease with increase of branching in carbon chain (because of decrease in van der
Waals forces with decrease in surface area.).
[1]
3. Among the four compounds (i) acetone, (ii) propanol, (iiii) methyl acetate and (iv)
propionic acid, the two that are isomeric are:
(A) Methyl acetate and acetone
(B) Methyl acetate and propanol
(C) Propionic acid and methyl acetate
(D) Propionic acid and acetone

c. Propionic acid and methyl acetate

Explanation:
Propionic acid and methyl acetate both have same molecular formula (C3H6O2) but
different functional groups, so they are isomers.

4. Phenol can be distinguished from ethanol by the reactions with .

(A) Br2/water. (B) Na.
(C) Neutral FeCl3. (D) All the above.

a. Br2/water.
c. Neutral FeCl3
Explanation:
Phenol reacts with bromine water to give a colourless tribromo derivative and gives a
violet coloured complex with FeCl3. Ethanol does not give these reactions.
5. Formation of 2-butene as a major product by dehydration of 2-butanol is according to:
(A) Markownikoff rule (B) Saytzeff rule
(C) Peroxide effect (D) Anti-markownikoff rule

b. Saytzeff rule
Explanation:
The formation of 2-butene as major product by dehydration of 2-butanol is according
to Saytzeff rule.
The minor product is 1-butene.
In this reaction, more substituted alkene is obtained as it is more stable.

6. Monochlorination of toluene in sunlight followed by hydrolysis with aq. NaOH yields.

(A) o-Cresol. (B) m-Cresol.
(C) 2, 4-Dihydroxytoluene. (D) Benzyl alcohol.

d. Benzyl alcohol.
Explanation:
Monochlorination of toluene in sunlight gives benzyl chloride. On hydrolysis with aq.
NaOH, benzyl chloride, shows nucleophilic substitution reaction to give benzyl
alcohol.

7. Which of the following order is true regarding the acidic nature of phenol?
(A) Phenol > O -cresol > O-nitrophenol
(B) Phenol > O -nitrophenol > O-cresol

[2]
 (C) O-cresol < phenol < O- nitrophenol
(D) Phenol < O-cresol < O-nitrophenol

c. O-cresol < phenol < O- nitrophenol

Explanation:
The following order is true regarding the acidic nature of phenol.
O-cresol < phenol < O- nitrophenol.
Phenols having electron withdrawing substituents such as nitro group are more
acidic due to delocalization of negative charge.
Phenols having electron releasing substituents such as alkyl group are less acidic as
negative charge is not delocalised.

8. Dehydration of alcohol is an example of which type of reaction?

(A) Substitution (B) Elimination
(C) Addition (D) Both B and C

b. Elimination
Explanation:
When heated with strong acids catalysts, alcohols typically undergo a 1,2-elimination
reactions to generate an alkene and water. Also known as dehydration since it
involves the removal of a molecule of water.

9. Ethers show dipolar nature due to the presence of .

(A) Central C atom (B) Central O atom
(C) Central N atom (D) None of these

b. Central O atom
Explanation:
Ethers have general structural formula R-O-R'. Hence all of them have the C-O bond.
We know that the C-O bond is polar due to the difference between the
electronegativities of carbon and oxygen. Hence, ethers show dipolar nature.

10. Correct order of acidic strength.

(A) I > II > III (B) II > III > I (C) I>III>II (D) III>II>I

b. II>III>I

[3]
 Explanation:
Acidic nature α−I

11. Among the three isomers of the nitrophenol, the one that is least soluble in water is:
(A) m-nitrophenol (B) o-nitrophenol
(C) p-nitrophenol (D) none of these

b. o-nitrophenol
Explanation:
Intramolecular hydrogen bonding in ortho-substituted nitrophenol reduces water
solubility and increases volatility.
Thus, o-nitrophenol is steam distillable while the isomeric p-nitrophenol is soluble in
water.

12. Which of the following substance will increase the acidity of phenol?
(A) Dil. H2SO4 (B) Dil. HCl
(C) Conc. H2SO4 (D) Conc. CH3COOH

a. Dil. H2SO4
Explanation:
Dilute H2SO4 will increase the acidity of phenol. This is because now phenol will be
easily able to donate H+ ion and delocalise its negative charge more efficiently. Also
addition of dilute H2SO4 which is itself an acid increases the acidity of phenol.
13. Which of the following is soluble in water?
(A) CS2 (B) C2H5OH (C) CCl4 (D) CHCl3

b. C2H5OH
Explanation:
Ethanol (C2H5OH) forms hydrogen bonding with water.
Hence, it is soluble in water.

14. Which of the following cannot be dissolved in alcohol?

(A) Dyes and drugs (B) Soaps and varnishes
(C) Resins and varnishes (D) Rubber and plastics

d. Rubber and plastics

Explanation:

[4]
 Rubber and plastic cannot be dissloved in alchol because of nonpolar nature of
rubber and plastics.

15. During dehydration of alcohols to alkenes by heating with conc. H2SO4, the initiation
step is:
(A) Elimination of water.
(B) Formation of an ester.
(C) Formation of carbocation.
(D) Protonation of alcohol molecule.

d. Protonation of alcohol molecule.

Explanation:
Dehydration of alcohol to alkene in presence of concentrated H2SO4 involves
following steps:
Thus, the initiation step is protonation of alcohol.

16. Phenol is less acidic than .

(A) Ethanol. (B) o-nitrophenol.
(C) o-methylphenol. (D) o-methoxyphenol.

b. o-nitrophenol.
Explanation:
In substituted phenols, the presence of electron withdrawing group such as nitro
group, enhances the acidic strength of phenol. This effect is more pronounced when
such a group is present at ortho and para positions. It is due to the effective
delocalisation of negative charge in phenoxide ion. On the other hand, electron
releasing groups, such as alkyl groups, in general, do not favour the formation of
phenoxide ion resulting in decrease in acid strength. Cresols, for example, are less
acidic than phenol.

17. Which of the following is most acidic?

(A) Benzyl alcohol. (B) Cyclohexanol.
(C) Phenol. (D) m-Chlorophenol

d. m-Chlorophenol
Explanation:
Alcohols are less acidic than phenol. Further electron withdrawing group (like - Cl)
increases the acidity of phenol, therefore, m-chlorophenol is most.

[5]
18. Glycol is a:
(A) Primary alcohol (B) Dihydric alcohol
(C) Secondary alcohol (D) Trihydric alcohol

b. Dihydric alcohol
19. The boiling point of methanol is greater than that of methyl thiol because:
(A) There is intramolecular hydrogen bonding in methanol and intermolecular hydrogen
bonding in methyl thiol.
(B) There is intermolecular hydrogen bonding in methanol and no hydrogen bonding in methyl
thiol.
(C) There is no hydrogen bonding in methanol and intermolecular hydrogen bonding in methyl
thiol.
(D) There is no hydrogen bonding in methanol and intramolecular hydrogen bonding in methyl
thiol.

b. There is intermolecular hydrogen bonding in methanol and no hydrogen bonding

in methyl thiol.
Explanation:
Methanol has high boiling point than methyl thiol because there is intermolecular
hydrogen bonding in methanol and no hydrogen bonding in methyl thiol.

20. The other name for Syngas is:

(A) Producer gas (B) Water gas
(C) Tear gas (D) Fuel gas

b. Water gas
Explanation:
Syngas is also called as water gas which is a mixture of carbon monoxide and
hydrogen.

21. Which of the following statement is not correct?

(A) Phenol is neutralised by sodium carbonate.
(B) Phenol is used to prepare analgesic drugs.
(C) Solubility of phenol in water is more than that of chlorobenzene.
(D) Boiling point of o-nitrophenol is lower than that of p-nitrophenol.

a. Phenol is neutralised by sodium carbonate.

Explanation:
Phenol does not react with Na2CO3 because it is weaker acid than carboxylic acid
and thereby do not have the strength to substitute or give away its H+ ions to that of
weak bases like sodium carbonate.
Phenol is used for the preparation of aspirin which is used as an analgesic as well as
antipyretic drugs.
Phenol is more soluble in water than chlorobenzene due to formation of H-bond with
water molecules.

[6]
 o-nitrophenol form intramolecular H−bonding while p-nitrophenol form
intermolecular H−bonding. Due to this, nature o-nitrophenol has a lower boiling
point than p-nitrophenol.

22. The correct order of boiling point for primary (1), secondary (2) and tertiary (3) alcohols
is:
(A) 1 > 2 > 3 (B) 3 > 2 > 1 (C) 2 > 1 > 3 (D) 2 > 3 > 1

a. 1>2>3
Explanation:
Alcohols with same molecular weight are expected to have almost same boiling
point however two more factors other than molecular weight are important, they are
namely H-bonding and surface area of molecule. Both these factors are least
in 3 alcohols and maximum in 1 alcohols. Hence, 3 alcohols have least boiling point
while 1 alcohols have maximum boiling point.

23. Acid catalysed hydration of alkenes except ethene leads to the formation of.
(A) Primary alcohol.
(B) Secondary or tertiary alcohol.
(C) Mixture of primary and secondary alcohols.
(D) Mixture of secondary and tertiary alcohols.

b. Secondary or tertiary alcohol.

Explanation:
Alkenes react with water in the presence of acid as a catalyst to form alcohol. In case
of unsymmetrical alkenes, OH is added to the carbon having fewer hydrogen atoms
according to Markovnikov's rule.
Hence, acid catalyzed hydration of alkenes except ethene leads to the formation of
secondary or tertiary alcohol. To obtain primary alcohol, hydroboration oxidation is
used.

24. Mark the correct statement:

(A) Water gas is used in the manufacture of methyl alcohol.
(B) Water gas has the highest calorific value.
(C) Water gas burns with luminuous flame.
(D) The production of water gas is exothermic process.

a. Water gas is used in the manufacture of methyl alcohol.

25. Electrophilic substitution reaction in phenol takes place at:
(A) Para position (B) Meta position
(C) Ortho position (D) Ortho and para position

d. Ortho and para position

Explanation:
Electrophilic substitution reaction in phenol takes place at ortho and para
position. −OH is an ortho para directing group.

[7]
 The electron density at ortho and para positions will be higher than the electron
density at meta position.

1. In these questions, a statement of assertion followed by a statement of reason is given.

Choose the correct answer out of the following choices.
a. Assertion and reason both are correct statements and reason is correct
explanation for assertion.
b. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
c. Assertion is correct statement but reason is wrong statement.
d. Assertion is wrong statement but reason is correct statement.
Assertion: P-Nitrophenol gives more electrophilic substituted compound than m-
methoxy phenol.
Reason: Methoxy group shows both +R and -I -effect.

d. Assertion is wrong statement but reason is correct statement.

Explanation:
ln p-nitrophenol, -NO2 group has -I effect, as a result of which electron density
decreases on the benzene ring, hence reactivity towards electrcphihc substitution
decreases. Methoxy group shows both +R (due to lone pair of electrons on O) and -
I effect (due to greater electronegativity of O). -OCH3 at meta-position shows only -
I effect but lesser than -I effect of -NO2 group.
2. Note: In the following questions a statement of assertion followed by a statement of
reason is given. Choose the correct answer out of the following choices.
i. Assertion and reason both are correct and reason is correct explanation of
assertion.
ii. Assertion and reason both are wrong statements.
iii. Assertion is correct statement but reason is wrong statement.
iv. Assertion is wrong statement but reason is correct statement.
v. Both assertion and reason are correct statements but reason is not correct
explanation of assertion.
Assertion: IUPAC name of the compound
CH3 − CH − O − CH2 − CH2 − CH3 is 2-Ethoxy-2-methylethane.
|
CH3
Reason: In IUPAC nomenclature, ether is regarded as hydrocarbon derivative in
which a hydrogen atom is replaced by —OR or —OAr group [where R = alkyl
group and Ar = aryl group]

iv. Assertion is wrong statement but reason is correct statement.

Explanation:
Correct assertion is the IUPAC name of the compound is 1-(2-propoxy) propane.

3. Note: In the following questions a statement of assertion followed by a statement of

reason is given. Choose the correct answer out of the following choices.

[8]
 i. Assertion and reason both are correct and reason is correct explanation of
assertion.
ii. Assertion and reason both are wrong statements.
iii. Assertion is correct statement but reason is wrong statement.
iv. Assertion is wrong statement but reason is correct statement.
v. Both assertion and reason are correct statements but reason is not correct
explanation of assertion.
Assertion: Addition reaction of water to but-1-ene in acidic medium yields butan-
1-ol.
Reason: Addition of water in acidic medium proceeds through the formation of
primary carbocation.

ii. Assertion and reason both are wrong statements.

Explanation:
Correct assertion: Addition reaction of water to but-1-ene in acidic medium yields
butan-2-01.
Correct reason: Addition of water in acidic medium proceeds through the
formation of secondary carbocation.

4. In these questions, a statement of assertion followed by a statement of reason is given.

Choose the correct answer out of the following choices.
a. Assertion and reason both are correct statements and reason is correct
explanation for assertion.
b. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
c. Assertion is correct statement but reason is wrong statement.
d. Assertion is wrong statement but reason is correct statement.
Assertion: With Br2-H2O, phenol gives 2, 4, 6-tribromophenol but with Br2-CS2, it gives
4-bromophenol as the major product.
Reason: In water, ionisation of phenol is enhanced but in CS2, it is greatly suppressed.

a. Assertion and reason both are correct statements and reason is correct
explanation for assertion.

1. Phenols do not undergo substitution of the -OH group like alcohols.

The C-O bond in phenols has some double bond character due to resonance and
hence cannot be easily cleaved by nucleophile. In contrast, the C-O bond in alcohols is a
pure single bond and hence can be easily cleaved by nucleophile.

2. Write the mechanism of hydration of ethene to yield ethanol.

The mechanism of hydration of ethene to form ethanol involves three steps.

Step 1:
Protonation of ethene to form carbocation by electrophilic attack of H3O+:
H2O + H+ −−→ H3O+

[9]
 Step 2:
Nucleophilic attack of water on carbocation:

Step 3:
Deprotonation to form ethanol:

3. The carbon-oxygen bond in phenol is slightly stronger than that in methanol. Why?

This can be explained as under:

i. In phenol, the conjugation of unshared electron pairs over oxygen with aromatic
ring results in partial double bond character in C-O bond.

In methanol, no such conjugation (resonance) is possible.

ii. In phenol, oxygen is attached to sp2 hybridised carbon while in methanol, oxygen
attached to sp2 hybridised carbon. An sp2 hybridised carbon is more
electronegative (because of greater 5-character) than sp3 hybridised carbon
atom. Therefore, the bond between oxygen and sp2 hybridised carbon is more
stable than the bond between oxygen and sp2, hybridised orbital.
4. Explain why p-nitrophenol is more acidic than phenol.

In substituted phenols, the presence of electron withdrawing groups such as nitro

groups, enhances the acidic strength of phenol. This effect is more pronounced when such
a group is present at ortho and para positions. It is due to the effective delocalisation of
negative charge in phenoxide ion.

5. o-nitrophenol is more acidic than o-methoxyphenol.

-R and -I effect of -NO2 group decreases the electron density in O-H bond and make
loss of proton easy in O-nitrophenol whereas +R effect of -OCH3 group increases the
electron density in O-H bond and makes release of proton difficult in o-methoxyphenol.
That is, why o-nitrophenol is stronger acid than o-methoxyphenol.

6. Write the equations involved in the following reactions:

i. Reimer - Tiemann reaction.
ii. Kolbe’s reaction.

[10]
 i. Reimer-Tiemann reaction

ii. Kolbe’s reaction

7. How will you bring the following conversions?

Phenol to benzyl alcohol.

8. Write the mechanism of acid dehydration of ethanol to yield ethene.

The mechanism of acid dehydration of ethanol to yield ethene involves the following three
steps:
Step 1:
Protonation of ethanol to form ethyl oxonium ion:

Step 2:
Formation of carbocation (rate determining step):

Step 3:

[11]
 Elimination of a proton to form ethene:

The acid consumed in step 1 is released in Step 3. After the formation of ethene, it is
removed to shift the equilibrium in a forward direction.

9. Out of 2-chloroethanol and ethanol which is more acidic and why?

The acidic character of alcohols is due to the polar nature of O-H bond. 2-
Chloroethanol, is more acidic due to -I effect of chlorine atom. It increases the polarity of
O- H bond and increases the acidic strength.

10. Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a

suitable method. Give reason.

Acid catalysed dehydration of primary alcohols to ethers occurs by SN2 reaction involving
nucleophilic attack by the alcohol molecule on the protonated alcohol molecule.

Under these conditions, 2° and 3° alcohols, however, give alkenes rather than ethers. The
reason being that due to steric hindrance, nucleophilic attack by the alcohol molecule on
the protonated alcohol molecule does not occur. Instead protonated 2° and 3° alcohols
lose a molecule of water to form stable 2° and 3° carbocation. These carbocations prefer
to lose a proton to form alkenes rather than undergoing nucleophilic attack by alcohol
molecules to form ethers.

Similarly, 3° alcohols give alkenes rather than ethers.

11. Out of o-nitrophenol and p-nitrophenol, which is more volatile? Explain.

Ortho nitrophenol is much more volatile in steam due to chelation. Intramolecular

hydrogen bonding is present in o-nitrophenol and intermolecular hydrogen bonding in p-
nitrophenol.

[12]
12. Alcohols react both as nucleophiles as well as electrophiles. Write one reaction of each
type and describe its mechanism.

Alcohols as nucleophiles: The bond between O-H is broken when alcohols react as
nucleophiles.

Alcohols as electrophiles: The bond C-O is broken when alcohols react as electrophiles.
Protonated alcohols react in this manner.

13. Give structures of the products you would expect when each of the following alcohol
reacts with
HBr
i. Butan-1-ol
ii. 2-Methylbutan-2-ol

i. CH3CH2CH2CH2OH + HBr −−−→ CH3CH2CH2CH2 Br

−H2O
Butan-1-ol 1-Bromobutane
ii. OH Br
| |
CH3 − CH2 − C − CH3 + HBr → CH3 − CH2 − C − CH3 + H2 O
| |
CH3 CH3
2-Methylbutan-2-ol(3∘) 2-Bromo-2-Methylbutane
14. Why is the C-O-H bond angle in alcohols slightly less than the tetrahedral angle whereas
the C-O-C bond angle in ether is slightly greater?

The bond angle in alcohol is slightly less than the tetrahedral angle (1090-28’). It is
due to the repulsion between the unshared electron pairs of oxygen.
In ethers, the four electron pairs, i.e., the two bond pairs and two lone pairs of electrons on
oxygen are arranged approximately in a tetrahedral arrangement. The bond angle is
slightly greater than the tetrahedral angle due to the repulsive interaction between the
two bulky (-R) groups.

15. How can phenol be converted to aspirin?

[13]
 Phenol is converted into salicylic acid.
The reaction is usually carried out by allowing sodium phenoxide to absorb carbon dioxide
and then heating the product to 400K and 4-7 atm pressure. First unstable intermediate is
formed which undergoes a proton shift to form sodium salicylate. The subsequent
acidification of sodium salicylate gives,

Then aspirin is obtained by acetylating salicylic acid with acetic anhydride and cons.
H2SO4.

1. Answer the following question:

An organic compound A having molecular formula C6H6O gives a characteristic colour
with aqueous FeCl3 solution. A on treatment with CO2 and NaOH at 400K under pressure
gives B which on acidification gives a compound C. The compound C reacts with acetyl
chloride to give D which is a popular pain killer. Deduce the structure of A, B, C and D.

2. Illustrate with examples the limitations of Williamson synthesis for the preparation of
certain types of ethers.

Williamson's synthesis is a versatile method for the synthesis of both symmetrical

and unsymmetrical ethers. However, for the synthesis of unsymmetrical ethers, a proper
choice of reactants is necessary. Since Williamson's synthesis occurs by SN2 mechanism
and primary alkyl halides are most reactive in Sn2 reaction, therefore, best yields of
unsymmetrical ethers are obtained when the alkyl halides are primary and the alkoxide
may be primary, secondary or tertiary. For example, tert-butylethyl ether is prepared by
treating ethyl bromide with sodium tert-butoxide.

[14]
 CH3 CH3
| δ+ δ−
Δ
|
− + + −
CH3 − C − O Na + CH3CH2 − Br −−→ CH3 − C − OCH2CH3 + Na Br
| |
CH3 CH3
(3∘ Alkoxide)
The above ether cannot be prepared by treating sodium ethoxide with tert-butyl chloride
or bromide since under these condition an alkene, i.e., isobutylene is the main product.
CH3
|
(CH3)3 − C − Br + C2H5O−Na+ −−−→ CH3 − C = CH2 + NaBr + C2H5 OH
2-Methylpropene
Aryl and vinyl halides cannot be used as substrates because they are less reactive in
nucleophilic substitution.

3. An organic compound ‘A’ having molecular formula C3H6 on treatment with aqueous
H2SO4 gives ‘B’ which on treatment with HCl/ ZnCl2 gives ‘C’. The compound C on
treatment with ethanolic KOH gives back the compound ‘A’. Identify the compounds A,
B, C.

A = CH3 − CH = CH2
Propene
B = CH3 − CH − CH3
|
OH
Propan-2-ol
Cl
|
C = CH3 − CH − CH3
2 − chloropropane
aq.H2SO4 HCl/ZnCl2
CH3 − CH = CH2 −−−−−−−−−→CH3 − CH − CH3 −−−−−−→
Propene (Hydration) |
A OH
Propan-2-ol
Ethanolic KOH
B
CH3 − CH − CH3 −−−−−−−−→ CH3 − CH = CH2
| Propene
Cl
2 − Chlorophane
C
4. Which is a stronger acid-phenol or cresol? Explain.

[15]
 All the cresols are weaker acids than phenols. Methyl group has +I effect (positive
inductive effect) as well as hyperconjugation effect but the hyperconjugation effect
predominates over the +I effect. Since both these effects increase the electron density in
the O-H bond and hence all the cresols are weaker acids than phenols
As hyperconjugation effect can operate only through ortho and para positions and not
through meta positions, therefore, meta-cresol is stronger acid than ortho and para-
cresols. However, due to stronger +I effect at ortho position than at para position (+I effect
decreases with distance), ortho-cresol is a weaker acid than para-cresol. Thus, the order of
acidic strength in increasing order is:
ortho-cresol < para-cresol < meta-cresol < phenol

5. Ortho and para nitrophenols are more acidic than phenol. Draw the resonance
structures of the corresponding phenoxide ions.

The electron withdrawing groups are more effective in increasing the acidic strength at
the para-position relative to the ortho position because of greater dispersal of charge on
oxygen atom.
Resonance structure of phenoxide ion:

Resonance structure of paranitrophenol:

Resonance structures of ortho nitro phenol:

Thus, presence of nitro group at ortho and para position incerease the acidic character.

[16]
6. Identify the product of the following reaction:
CH3
|
NaOH
CH3 − C − CH2 − Br −−−−−→
| Δ
CH3

Neopentyl bromide ionises to form first a 1° carbocation which rearranges to form the
more stable 3° carbocation. This is attacked by weak nucleophile ethanol followed by loss
of proton to yield ethyl tert-pentyl ether.

7. Arrange water, ethanol and phenol in increasing order of acidity and give reason for
your answer.

Phenol > Water > Ethanol

An alkoxide ion is a better proton acceptor than hydroxide ion, which suggests that
alkoxides are stronger bases (sodium ethoxide is a stronger base than sodium hydroxide).
The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger
acids than alcohol and water.
The ionisation of an alcohol and a phenol takes place as follows:

In alkoxide ion, the negative charge is localised on oxygen while in phenoxide ion, the
charge is delocalised. The delocalisation of negative charge (structures I-V) makes.

[17]
8. Give two reactions that show the acidic nature of phenol. Compare acidity of phenol
with that of ethanol.

The acidic nature of phenol can be represented by the following two reactions:
i. Phenol reacts with sodium to give sodium phenoxide, liberating H2.

ii. Phenol reacts with sodium hydroxide to give sodium phenoxide and water as
byproducts.

The acidity of phenol is more than that of ethanol. This is because after losing a
proton, the phenoxide ion undergoes resonance and gets stabilized whereas
ethoxide ion does not.

9. a. Draw the structures of all isomeric alcohols of molecular formula C5H12O and
give their IUPAC names.
b. Classify the isomers of alcohols in question 11.3 (i) as primary, secondary and
tertiary alcohols.

a. Eight isomeric alcohols are possible:

i. CH3 − CH2 − CH2 − CH2 − CH2 − OH
Pentan-1-ol(1∘)
ii. CH3 − CH2 − CH − CH2 − OH
|
CH3
2-Methylbutan-1-ol(1∘)
iii. CH3 − CH − CH2 − CH2 − OH
|
CH3
3-Methylbutan-1-ol(1∘)

[18]
 iv. CH3
|
CH3 − C − CH2 − OH
|
CH3
2,2-Dimethylpropan-1-ol(1∘ )
v. OH
|
CH3 − CH2 − CH2 − CH − CH3
Pentan-2-ol(2∘ )
vi. CH3 OH
| |
CH3 − CH − CH − CH3
3-Methylbutan-2-ol(2∘ )
vii. OH
|
CH3 − CH2 − CH − CH2 − CH3
Pentan-3-ol(2∘ )
viii. OH
|
CH3 − CH2 − C − CH3
|
CH3
2-Methylbutan-2-ol(3∘)
b. Primary alcohol: Pentan-1-ol; methyl butan-1-ol; 3-methyl-1-ol; 2,2Dimethyl
propan-t-ol.
Secondary alcohol: Pentan-2-ol; 3-methylbutan-2-ol; pentan-3-ol.
Tertiary alcohol: 2-methylbutan-2-ol.

1. Read the passage given below and answer the following questions:
Dehydration of alcohols can lead to the formation of either alkenes or ethers. This
dehydration can be carried out either with protonic acids such as cone.H2SO4, H3PO4 or
catalysts such as anhydrous ZnCl2 or Al2O3. When primary alcohols are heated with
cone. H2SO4 at 433-44 K, they undergo intramolecular dehydration to form alkenes.
Secondary and tertiary alcohols undergo dehydration under milder conditions. The
ease of dehydration of alcohols follows the order: 3º > 2º > 1º.
The dehydration of alcohols always occurs in accordance with the Saytzeff's rule.
Primary alcohols when heated with protic acid at 413K, gives dialkyl ether.
conc. H2SO4
CH3CH2OH −−−−−−−→ CH2 = CH2 + H2O
433.433K
conc. H2SO4
2CH3CH2OH −−−−−−−→ CH3CH2 − O − CH2CH3 + H2O
433K

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The following questions are multiple choice questions. Choose the most appropriate
answer:
i. Which one of the following alcohols undergoes acid-catalysed dehydration to
alkenes most readily?
a. (CH3)2CHCH2OH
b. (CH3)3COH
c. CH3CHOHCH3
d. CH3CH2CH2OH
ii. Dehydration of alcohol is an example of which type of reaction?
a. Substitution.
b. Elimination.
c. Addition.
d. Rearrangment.
iii. The alcohol which does not give a stable compound on dehydration is:
a. Ethyl alcohol.
b. Methyl alcohol.
c. N-propyl alcohol.
d. N-butyl alcohol.

iv. The most stable product (s) is/ are:

a.

b.

c. Both (a) and (b)

d. None of these.

v. The product of the reaction

i. (b) (CH3)3COH
Explanation:
The order of dehydration of alcohols is 3º > 2º > 1º.
ii. (b) Elimination.
Explanation:
The dehydration of alcohol is an example of elimination reaction.
iii. (b) Methyl alcohol.

[20]
 Explanation:
Dehydration of CH3OH will give methylene (a carbene) which is unstable.
H2SO4
CH3OH −−−−→ :CH2 + H2 O
(unstable)
iv. (a)

Explanation:

v. (c)

Explanation:

2. Read the passage given below and answer the following questions:
A compound (X) containing C, H and O is unreactive towards sodium. It also does not
react with Schiff s reagent. On refluxing with an excess of hydroiodic acid, (X) yields
only one organic product ( Y). On hydrolysis, (Y) yields a new compound (Z) which can
be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on
oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight
of this acid is 60.
The following questions are multiple choice questions. Choose the most appropriate
answer:
i. The compound (X) is an:
a. Acid.
b. Aldehyde.
c. Alcohol.

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 d. Ether.
ii. The IUPAC name of the acid formed is:
a. Methanoic acid.
b. Ethanoic acid.
c. Propanoic acid.
d. Butanoic acid.
iii. Compound (Y) is:
1. Ethyl iodide.
2. Methyl iodide.
3. Propyl iodide.
4. Mixture of (a) and (b).
iv. Compound (Z) is:
a. Methanol.
b. Ethanol.
c. Propanol.
d. Butanol.
v. Compound (X) on treatment with excess of Cl2 in presence of tight gives:
a. ∝ − Chlorodiethyl ether.
b. ∝, ∝′ − Dichlorodiethyl ether.
c. Perchlorodiethyl ether.
d. None of these.

i. (d) Ether.
Explanation:
Since the compound X is unreactive towards sodium so it is neither an acid nor an
alcohol. Since the compound X is unreactive towards Schiff's base so it is not an
aldehyde.
The compound X forms only one product on reaction with excess HI, indicates that
the compound X may be ether.
ii. (b) Ethanoic acid.
Explanation:
The reactions can be written as:

Since the equivalent weight of carboxylic acid is 60. So, it must be CH3COOH i.e.,
ethanoic acid.
iii. (a) Ethyl iodide.
Explanation:
The alcohol Z in that case should be C2H5OH and the compound Y should be ethyl
iodide. X is therefore diethyl ether (C2H5 — O — C2H5)

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 iv. (b) Ethanol.
v. (c) Perchlorodiethyl ether.
Explanation:
In the presence of light and excess of chlorine, all the hydrogen atoms of diethyl
ether are substituted to give perchlorodiethyl ether.
hu
CH3CH2 − O − CH2CH3 + 10Cl2 −→
(excess)
CCl3CC2 − O − CCl2 − CCl3 + 10HCI
Perchlorodierhyl ether
3. Read the passage given below and answer the following questions:
An organic compound (A) having molecular formula C6H6O gives a characteristic
colour with aqueous FeCl3 solution. (A) on treatment with CO2 and NaOH at 400K under
pressure gives (B), which on acidification gives a compound (C). The compound (C)
reacts with acetyl chloride to give (D) which is a popular pain killer.
The following questions are multiple choice questions. Choose the most appropriate
answer:
i. Compound (A) is:
a. 2-Hexanol.
b. Dimethyl ether.
c. Phenol.
d. 2-Methyl pentanol.
ii. Compound (C) is:
a. Salicylic acid.
b. Salicyladehyde.
c. Benzoic acid.
d. Benzaldehyde.
iii. Number of carbon atoms in compound (D) is:
a. 7
b. 6
c. 8
d. 9
iv. The conversion of compound (A) to (C) is known as:
a. Reimer-Tiemann reaction.
b. Kolbe's reaction.
c. Schimdt reaction.
d. Swarts reaction.
v. Compound (A) on heating with compound (C) in presence of POCl3 gives a
compound (D) which is used:
a. In perfumery as a ftavouring agent
b. As an antipyretic
c. As an analgesic
d. As an intestinal antiseptic.

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 i. (c) Phenol.
Explanation:

ii. (a) Salicylic acid.

iii. (d) 9
Explanation:

It has 9 C-atoms.
iv. (b) Kolbe's reaction.
Explanation:
Sodium phenoxide when heated with CO2 at 400K under a pressure of 4-7 atm
followed by acidification gives 2-hydroxybenzoic acid (salicylic acid) as the main
product along with a small amount of 4-hydroxybenzoic acid. This reaction is called
Kolbe's reaction.
v. (d) As an intestinal antiseptic.
Explanation:
 Salol is used as an intestinal antiseptic.

1. Answer the following question:

Write mechanism of the reaction of HI with methoxymethane.

The cleavage of methoxymethane with HI follows SN2 mechanism.

Step I:

Step II:

If excess of HI is used, methyl alcohol formed in step II further reacts with another
molecule of HI to form CH3I.
Step III:

2. An aromatic compound ‘A’ on treatment with CHCl3/ KOH gives two compounds ‘B’ and
‘C’. Both B and C give the same product ‘D’ when distilled with zinc dust. Oxidation of D
gives E having molecular formula C7H6O2. The sodium salt of E on heating with
sodalime gives F which may also be obtained by distilling A with zinc dust. Identify A to F.
3. Answer the following question:
How will you convert phenol to benzoic acid?

4. a. The acid strength of alcohols decreases in the order

b. Phenol is more easily nitrated than benzene.

a. The acidic character of alcohols is due to the polar nature of O-H bond. As alkyl
groups have +I effect, therefore, electron density on oxygen increases from 1 to
3° alcohols. In other words, the O-H bond in 3° alcohols is most polar whereas it is
least polar in 1° alcohols. Thus, the acid strength of alcohols follows the order

b. Nitration involves attack of electrophile nitronium (NO2) ion on benzene ring. Due
to +R effect of O-H group electron density increases at ortho and para position in
phenol. Therefore, phenol is more easily nitrated than benzene.
5. Identify A and B in the following reactions:
a.

Cu,573k CH3 MgBr

b. C2H5OH −−−−→ A −−−−−→ B
H2O/H+
a.

b.

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