Chemistry (F.Sc.2) Chapter # 11 Exercise Solved - Malik Xufyan 0313-7355727

1. Malik Xufyan F.Sc.ll (Chemistry)
03137355727 Ch.No. 11 (Exercise)
www.onlychemistrydiscussion.blogspot.com
Chapter No.11: Alcohol, Phenol & Ether
Exercise
Q 6. What is fermentation? What compounds may be obtained industrial scale by
fermentation.
The biochemical process in which starch and sugars are converted into ethyl alcohol by
yeast is called fermentation.
Following compounds can be prepared by fermentation: Ethyl alcohol, acetic acid etc.
Q 10. How will you distinguish b/w
(i) An alcohol and a phenol
These can be distinguish by following ways.
 Alcohol is neutral while phenol is acidic.
 Phenol gives white ppt with Br2 water while alcohol does not.
OH
+ 3Br2
H2O
Br Br
OH
Br
+ 3HBr
2,4,6-tribromophenol
Phenol gives deep purple color with FeCl3 while alcohol does not.
(ii) An alcohol and an ether
These can be distinguish by following test.
Alcohol evolve H2 gas with Na metal while ether does not.
2R-OH + 2Na 2R-O-
Na+
+ H2
(iii) Methanol and ethanol
These can be distinguish by iodoform test.
Ethanol gives yellow ppt. of iodoform on reacting with NaOH and I2.
Methanol does not give yellow ppt. of iodoform on reactiong with NaOH and I2.
C2H5OH + 4I2 + 6NaOH CHI3 + HCOONa + 5NaI + 5H2O
Iodoform(yellow ppt.)
CH3OH + I2 + NaOH No yellow ppt.
(iv) A tertiary alcohol and a primary alcohol
These can be distinguish by Lucas test.
When Lucas reagent (HCl + ZnCl2) is added to an alcohol.
Tertiary alcohol forms oily layer of alkyl halides immediately.
While primary alcohol forms oily layer only on heating.

2. Malik Xufyan F.Sc.ll (Chemistry)
03137355727 Ch.No. 11 (Exercise)
www.onlychemistrydiscussion.blogspot.com
R CH2-OH + HCl
ZnCl2
heat
R CH2-OH + H2O
Primary alcohol
C
R
R
R OH + HCl
ZnCl2
immediately
C
R
R
R Cl + H2O
Tertiary alcohol
(v) 1-propanol and 2-propanol
1-Propanol is primary alcohol while 2-propanol is secondary alcohol. These can be
distinguish by Lucas test.
When Lucas reagent (HCl + ZnCl2) is added to an alcohol.
2-propanol forms oily layer of alkyl halides within 5-10 mins.
H3C CH-OH + HCl
CH3
ZnCl2
5-10 mins
H3C CH-Cl + H2O
CH3
2-Propanol
While 1-propanol forms oily layer only on heating
H3C-CH2-CH2-OH + HCl
1-propanol
ZnCl2
heat
H3C-CH2-CH2-Cl + H2O
Q 11. Give reasons for the followings:
(i) Ethyl alcohol is a liquid while ethyl chloride is a gas.
Ethyl chloride has weak dipole-dipole forces while ethanol has strong hydrogen bonding.
H O H H O H
O
C2H5 C2H5 C2H5
hydrogen bonding
Due to strong hydrogen bonding in ethanol, its molecules are tightly held together. Thus,
ethanol is a liquid while ethyl chloride is gas.
(ii) Ethanol has higher boiling point than diethyl ether.
Ethanol has strong hydrogen bonding , while diethyl ether have weak vander waal’s
forces.
H O H H O H
O
C2H5 C2H5 C2H5
hydrogen bonding
Due to strong hydrogen bonding in ethanol, its molecules are tightly held together .

3. Malik Xufyan F.Sc.ll (Chemistry)
03137355727 Ch.No. 11 (Exercise)
www.onlychemistrydiscussion.blogspot.com
Thus, it is difficult to boil ethanol than diethyl ether. Hence, ethanol has higher boiling
point than diethyl ether.
(iii) Absolute alcohol cannot be prepared by fermentation process.
Absolute alcohol cannot be prepared by fermentation process. It is because at high conc.
of alcohol, enzyme of yeast becomes inactive and process stops.
Actually, alcohol obtained by fermentation process is only up to 12%. This alcohol is
further concentrated by distillation to about 95% called rectified spirit. Rectified spirit
is further distilled with lime to give absolute alcohol.
(iv) Ethanol gives different products with conc. H2SO4 under different
conditions.
Ethanol gives two types of product in different conditions.
High temperature, low alcohol conc.
H3C-CH2-OH
conc. H2SO4
180oC
H2C=CH2 + H2O
Low temperature, high alcohol conc.
H3C-CH2-OH conc. H2SO4
180o
C
+
H3C-CH2-OH
H3C-CH2
H3C-CH2
O + H2O
Diethyl ether
(v) Water has higher boiling point than ethanol.
In water, two hydrogen bonds are formed per molecule while in ethanol only one
hydrogen bond is formed per molecule. Thus due to extensive hydrogen bonding in H2O,
its boiling point is greater than ethanol.
H O H H O H
O
C2H5 C2H5 C2H5
hydrogen bonding
Q 12. How will you convert
(i) Methanol into Ethanol
H3C-OH + HCl
ZnCl2/heat
CH3Cl + H2O
2H3CCl + 2Na
ether
H3C-CH3 + 2NaCl
H3C-CH3 + Cl2
light
H3C-CH2-Cl + HCl
H3C-CH2-Cl + KOH
Aqueous
H3C-CH2-OH + KCl
ethanol
methanol
(ii) Ethanol into methanol

4. Malik Xufyan F.Sc.ll (Chemistry)
03137355727 Ch.No. 11 (Exercise)
www.onlychemistrydiscussion.blogspot.com
H3C-CH2-OH + HCl
ZnCl2/heat
CH3-CH2-Cl + H2O
H3C-CH2-Cl + KOH
Aqueous
H2C=CH2 + KCl + H2O
H2C=CH2
(i) O3
(ii) Zn/H2O
2H C
O
H
Formaldehyde
H C
O
H + H2
Ni/heat
H3C-OH
methanol
(iii) Ethanol into isopropyl alcohol
H3C-CH2-OH + [O] K2Cr2O7
H2SO4
H3C C H
O
Methanol Acetaldehyde
CH3 Mg Br + C O
Ether
H3C-C-O-MgBr
H-OH
H
H3C-C-OH + Mg
Br
OH
2-Propanol
(isopropyl alcohol)
H3C
H
H3C
H
H
H3C
Acetaldehyde
(iv) Formaldehyde into ethyl alcohol
CH3
Mg Br + C O
Ether
CH3-C-O-MgBr
H-OH
H
CH3-C-OH + Mg
Br
OH
Ethanol
H
H
H
H
H
H
(v) Acetone into ethyl alcohol

5. Malik Xufyan F.Sc.ll (Chemistry)
03137355727 Ch.No. 11 (Exercise)
www.onlychemistrydiscussion.blogspot.com
H3C C CH3 + H2
O
H3C CH CH3
OH
H3C C H
O
Acetaldehyde
Acetone
Ni
H3C CH CH3
OH
60% H2SO4
100o
C
H3C-CH=CH2 + H2O
H3C-CH=CH2
(i) O3
(ii) Zn/H2O
H3C C H + H2
O
Acetaldehyde
H C H
O
Formaldehyde
+
Ni
H3C-CH2-OH
Ethanol
Q 15. Arrange the following compounds in order of their increasing acid strength
and give reasons.
H2O,C2H5OH,C6H5OH,C6H5COOH
C6H5COOH > C6H5OH >H2O > C2H5OH