Properties of Alcohols and Phenols

 Some Industrial forms:
(a) 95.6% v/v or 95% w/w ethyl alcohol – H₂O mixture is azeotropic mixture.
(b) 90% ethanol + 9% CH₃OH + 1% petroleum oil + violet dye → Methylated spirit.
(c) 100% pure C₂H₅OH is called absolute alcohol.
(d) About 20% ethanol +80% gasoline (v/v) mixture is used in engines of air-crafts. This added alcohol is called power alcohol.
(e) A mixture of C₂H₅OH, (CH₃COO)₂Ca and C₁₇H₃₅COOH is solid and is called as solid (fuel) alcohol.

Properties of Alcohols, Phenol and Glycol:
Physical properties:
(a) State: up to C₁₁, alcohols are liquids while higher members are waxy solids.
(b) Toxic nature: Though all alcohols are toxic, methanol is deadly poisonous and can cause blindness and death.
(c) Solubility: Lower members are easily miscible with water while for higher members solubility decreases due to increase in size of hydrophobic "R" part.
solubility of isomeric alcohols increases with increase in branching due to decrease in relative volume of hydrophobic R part 1° < 2° < 3°
(d) Boiling points: Increase in carbon chain increases boiling point by 18-20°C per c-atom.
CH₃OH (64.5°C) < C₂H₅OH (78.3°C) < CH₃–CH₂–CH₂OH (97°C) < CH₃CH₂–CH₂–CH₂–CH₂OH (118°C)

Chemical properties:
A. Cleavage of O–H bond
Phenols are more acidic than alcohols because the phenol ion is resonance stabilized.
(a) Reaction with Na: All alcohols react with Na to produce H₂ gas. 2° alcoholic group of glycerol does not react.
(b) Reaction with NaOH: Only phenol reacts showing it to be most acidic among all these compounds.
(c) Reaction with acids: Ester with fruity smell are produced. Order of reactivity:
     (1) CH₃OH > 1° > 2° > 3°
     (2) HCOOH > CH₃COOH >....> R₂CH–COOH > R₃C–COOH

(i) In the presence of H₂SO₄, as catalyst, 67% completion of reaction takes place. 'OH' of acid goes to give water.
(ii) In the presence of HCl gas, the reaction, Fischer-spier reaction, goes to approximately 100% completion.
\tt R-OH+R'COOH\xrightarrow{HCl_{(g)}}R'COOR+H_2O
(iii) Acid chloride and acid anhydride also produce esters. The reaction of benzoyl chloride in the presence of dil NaOH is called Schotten Baumann reaction.
(a) Heating of phenyl benzoate in the presence of anhydrous AlCl₃, produces ketones. The rearrangement is called

Fries rearrangement.

(iv) Reaction of ethylene glycol with p-phthalic acid or its dimethyl ester, followed by polymerisation gives polyester, terylene while o-phthalic acid, the product is glyptal (used in paints and varnishes).
(d) \tt ROH(or\ ArOH)\xrightarrow[HBF_4]{CH_2N_2}(R/Ar)-O-CH_3
B. Cleavage of C-O Bond:
(a) \tt R-OH_{(g)}+NH_{3(g)}\xrightarrow[633K]{Al_2O_3(or)ThO_2}R-NH_2+R_2NH+R_3N(Industrial\ method)
(b) \tt C_6H_5OH+NH_3\xrightarrow[ZnCl_2/press]{573K}C_6H_5NH_2(Aniline)+H_2O(Bucherer\ reaction)
(c) \tt C_6H_5OH\xrightarrow[\Delta]{Zn(dust)}C_6H_6(Benzene)+ZnO(Reduction\ reaction)
(d)(i) Reaction of HX (order HI > HBr > HCl), HCl/ZnCl₂, PCl₅, PCl₃, SOCl₂ produce corresponding halogen compounds.
(ii) The reactions of PCl₅ and SOCl₂ (Darzen process, best for 1° alcohol) are S_N1 reaction. No rearrangement take place in the absence of Pyridine but approximately 100% Walden inversion takes place in the presence of pyridine.
(iii) Order of reactivity of alcohols is allyl ≅ benzyl > 3° > 2° > 1° > CH₃OH
(iv) 1° alcohols and CH₃OH react with HX through S_N² mechanism.
(v) 3°, 2° and hindered 1° alcohols follow S_N¹ mechanism.
(e) Reaction of HCl/ZnCl₂ (Lucas reagent) called as Groove reaction gives immediate white turbidity with 3° alcohols, it takes 2 to 10 minutes for 2° alcohols while 1° alcohols react only on heating. This reaction is also known as Lucas test. 3° alcohols follow S_N¹ mechanism even in the absence of ZnCl₂.
(f) With HI (or) P(red)/I₂, when ethylene glycol reacts, the product is ethene excess of HI may convert it to ethyl iodide.

C. Dehydration:
(i) Ease of dehydration of alcohols is in the order : 3° > 2° > 1°, conjugation makes the reaction still easier. Saytzeff rule is followed. When dehydration is in one molecule, it is E₁ elimination. 3°–alcohols are also dehydrated easily because 3° carbocation is formed as intermediate.
(a)
(b)
(c) \tt CH_3CH_2-OH \xrightarrow[(or)H_2SO_4/333-353K]{Al_2O_3/575-623K}C_2H_4+H_2O

D. Iodoform Test (Preparation of haloforms):
The reaction is given by compounds containing ketonic (or) methyl carbinol group
(a) \tt CH_3CH_2-OH+4I_2+6NaOH\xrightarrow{\Delta}CHI_3(Iodoform\ yellow\ solid)+HCOONa+5H_2O+5NaI

E. Acetal formation:
Monohydric alcohols react with aldehydes easily to produce hemiacetals and then acetals in the presence of HCl gas. Ketones give poor yield of hemiketals and ketals. Polyhydric alcohols react with aldehydes and ketones both to produce cyclic acetals and cyclic ketals repectively.
(a)
(c) If NaOH is used, only hemiacetal is formed.
(d) Acetals and hemiacetals can be hydrolysed by dil HCl
(e) Cyclic structures of monosaccharides are hemiacetals while those of disaccharides are acetals.
G. Oxidation:
(i) Oxidation of monohydric alcohols:
(a) \tt R-CH_2-OH(1^0alcohol)\xrightarrow{Cu/573K}R-CHO(Aldehyde)+H_2(Dehydration)
(b) \tt CH_3OH+\frac{1}{2}O_2\xrightarrow{Cu/823K}HCHO+H_2O
(c) \tt CH_3-CH_2-OH+O_2\xrightarrow[bacteria]{Mycodermaceti}CH_3COOH+H_2O(Quick\ vinegar\ process)

Trick for oxidation (List of reagents)
(f) Following chemicals oxidise 1° alcohols to acids, 2° alcohols to ketones
(i) 1% alkaline kMnO4 (Bayer's reagent)
(ii) K₂Cr₂O₇/H₂SO₄ (dil), i.e, H₂CrO₄ (hypothetical acid)
(iii) KMnO₄/H₂SO₄ (dil)
(iv) CrO₃ / glacial CH₃COOH
All these reagents can oxidise ketones under vigorous conditions to smaller acids.
(g) Following chemicals oxidise 1° alcohols to corresponding aldehydes (not to acids) and 2° alcohols to ketones
(i) CrO₃/H₂SO₄ dil/Aq.acetone (Jone's reagent)
(ii) PCC : Pyridinium chlorochromate (C₅H₅NH⁺) \tt (ClCrO_3^{^-}) in CH₂Cl₂ (Sarett-collin reagent)
(iii) Pyridine + HCl + CrO₃ (Corey's reagent)
(iv) PDC: Pyridinium dichromate (C₅H₅N⁺H)2 \tt (Cr_2O_7^{2-})
Pyridine + K₂ Cr₂O₇ + H₂SO₄ dil
\tt R-CH_2OH\xrightarrow[\Delta]{(i)or(ii)or(iii)}R-CHO
NBS also oxidises 1° alcohols to aldehydes and 2° alcohols to ketones.
(h) Tertiary butoxide of aluminium [(CH₃)₃CO]₃ Al in acetone (or) cyclohexanone converts 1° alcohols to aldehydes and 2° alcohols to ketones at the cost of acetone or cyclohexanone that is reduced to propan-2-ol or cyclohexanol. The reaction is known as oppenauer oxidation.
(i) MnO₂ is used to oxidise allylic and benzylic alcohols to corresponding aldehydes and ketones.
(a) \tt CH_2=CH-CH_2OH\xrightarrow{MnO_2/\Delta}CH_2=CH-CHO
(j) N₂O₄/CHCl₃, Field's reagent converts only benzylic alcohols to corresponding aldehydes and ketones

Oxidation of Phenol:
(a)

Properties of Phenol due to benzene ring:

Distinctions among 1°, 2° and 3° alcohols:
Victor Meyer's test (Red-blue test)

Reagent Used	1° Alcohol R–CH2–OH	2° alcohol R2CH–OH	3° alcohol R3 C–OH
P/I2	R–CH2–I	R2CHI	R3C–I
AgNO2	RCH2NO2
HNO2 (NaNO2/HCl)			No reaction
NaOH		No reaction Blue colour retained	No reaction No colour

Solubility of Alcohols:
(a) Solubility of alcohols increases with increase in branching and degree of alcohol.
n-butyl alcohol < isobutyl alcohol < sec-butylalcohol < ter-butyl alcohol
(b) Boiling points of alcohols decrease with increase in degree of alcohol and increase with increase in length of the chain (hydrocarbon part)
methanol < ethanol < propan-2-ol < propan-1-ol