Alcohols are organic compounds with -OH as the main functional group.In this post we will study about the classification, preparation and reactions of alcohol; preparations and reactions of phenol.
After completing this section don’t forget to complete the question answers and Practice Set of this chapter. The links are at the bottom.
Classification of Alcohols:
Monohydric alcohols:
Compounds which contain only one -OH group.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 2 Monohydric alcohols:](https://www.allaboutchemistry.net/storage/2020/07/image-181.png)
- If carbon which contains -OH group, also possesses 2 directly bonded H atom, it is called 10
- If carbon which contains -OH group, also possesses 1 directly bonded H atom, it is called 20
- If carbon which contains -OH group, also possesses no directly bonded H atom, it is called 30
Dihydric alcohols:
Compounds which contains two -OH groups.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 3 Dihydric alcohols:](https://www.allaboutchemistry.net/storage/2020/07/image-182.png)
Trihydric alcohols:
Compounds which contains three -OH groups.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 4 Trihydric alcohols](https://www.allaboutchemistry.net/storage/2020/07/image-183.png)
Allylic alcohols:
If -OH group is present in the allylic position.(sp3 carbon attached to sp2 carbon)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 5 Allylic alcohols](https://www.allaboutchemistry.net/storage/2020/07/image-180.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 6 Allylic alcohols](https://www.allaboutchemistry.net/storage/2020/07/image-184.png)
Benzylic alcohols:
When -OH group is attached to the benzylic carbon (Ph-CH2-)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 7 Benzylic alcohols:](https://www.allaboutchemistry.net/storage/2020/07/image-186.png)
Phenols:
When -OH group is directly attached with Benzene group, it is called phenol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 8 Phenols and Phenolic compounds](https://www.allaboutchemistry.net/storage/2020/07/image-187.png)
Preparation of Alcohols
1.From alkenes:
Alkenes when reacted with concentrated sulphuric acid followed by water, alcohol is produced following Markownifoff’s Rule.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 9 Preparation of alcohol from alkenes](https://www.allaboutchemistry.net/storage/2020/07/image-194.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 10 Preparation of alcohol from alkenes](https://www.allaboutchemistry.net/storage/2020/07/image-190.png)
At first add +ve ion from the acid ion to that C atom which contain max no of H atom in a double bond. Then add the anion from the nucleophile.[From OH– and OD–, OD– always adds]
Special case:
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 11 Hydride Shift](https://www.allaboutchemistry.net/storage/2020/07/image-191.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 12 Methyl Shift](https://www.allaboutchemistry.net/storage/2020/07/image-192.png)
2.From alkenes:
When alkenes are reacted with boron trihydride in Tetrahydrofuran media followed by alkaline oxidation by hydrogen peroxide, alcohol is produced following anti markownikoff’s rule.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 13 Preparation of alcohol from alkenes, Anti Markownikoff's Rule](https://www.allaboutchemistry.net/storage/2020/07/image-193.png)
My Suggestion: If you want to produce alcohol of lower degrees follow anti markownokoff’s rule. Propene when subjected to acidic hydrolysis, 2-Propanol is produced. But when treated with boron trihydride in Tetrahydrofuran media followed by alkaline oxidation by hydrogen peroxide, 1-Propanol is produced.
3. From alkyl halides:
Alkyl halides when reacted with Aq KOH or Aq NaOH or moist Ag2O , halogen is substituted with -OH group to produce alcohol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 14 preparation of alcohol from alkyl halide](https://www.allaboutchemistry.net/storage/2020/07/image-196.png)
- For a particular alkyl group, RCl <RBr< RI
- For a particular halogen atom, 30< 20< 10 [For SN2]
4.Reduction of aldehydes, ketones, acid, esters, acid halides:
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 15 Preparation of alcohol from ketone](https://www.allaboutchemistry.net/storage/2020/07/image-197.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 16 Preparation of alcohol from aldehyde](https://www.allaboutchemistry.net/storage/2020/07/image-198.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 17 Preparation of alcohol from carboxylic acid and ester](https://www.allaboutchemistry.net/storage/2020/07/image-199.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 18 Preparation of alcohol from acid chloride](https://www.allaboutchemistry.net/storage/2020/07/image-200.png)
Reducing agents:
- LiAlH4 and H3O+ – can be used in all cases
- Na/CH3CH2OH – can be used in all cases
- NaBH4/CH3CH2OH – can be used for ketone, aldehyde, and acid halide only
5.By Grignard:
Formaldehyde when treated with Grignard reagent followed by acidic hydrolysis, 10 alcohol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 19 Formation of primary alcohol from formaldehyde using grignard reagent](https://www.allaboutchemistry.net/storage/2020/07/image-201.png)
Aldehyde except for formaldehyde when treated with Grignard reagent followed by acidic hydrolysis, 20 alcohol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 20 Formation of secondary alcohol from aldehyde using grignard reagent](https://www.allaboutchemistry.net/storage/2020/07/image-202.png)
Ketone when treated with Grignard reagent followed by acidic hydrolysis, 30 alcohol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 21 Preparation of tertiary alcohol from ketyone](https://www.allaboutchemistry.net/storage/2020/07/image-203.png)
Acid chlorides and esters when treated with Grignard reagent followed by acidic hydrolysis, 30 alcohol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 22 Preparation of tertiary alcohol from ester and acid halide](https://www.allaboutchemistry.net/storage/2020/07/image-204.png)
6.From amines:
Primary amines when treated with sodium nitrite and hydrochloric acid, -NH2 group get substituted with -OH group to produce alcohol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 23 preparation of alcohol from amines](https://www.allaboutchemistry.net/storage/2020/07/image-205.png)
7.From Ester
Esters when hydrolyzed, produce carboxylic acid and alcohol. The hydrolysis can be done in both acidic and alkaline medium. If hydolysis is done by NaOH solution, a sodium salt of carboxylic acid is produced. The sodium salt of higher carboxylic acid(fatty acid) is called soap. That’s why this reaction is called a saponification reaction.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 24 image 206 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-206.png)
Reactions of alcohol:
1.Preparation of sodium alkoxides:
Alcohol when reacted with metallic sodium, sodium alkoxide is produced along with hydrogen. This reaction proves the acidic nature of alcohol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 25 Reaction of alcohol with sodium](https://www.allaboutchemistry.net/storage/2020/07/image-207.png)
2.Preparations of alkanes:
Alcohol act as a proton donor. When grignard reagent react with alcohol, alkane is magnesium alkoxy halide is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 26 Preparation of alkane from alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-208.png)
3.Preparation of esters:
Alcohol when warmed with carboxylic acid in presence of conc. sulphuric acid , produce ester and water. This process is called esterification reaction. Esters possess fruity smell.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 27 Esterfication Reaction](https://www.allaboutchemistry.net/storage/2020/07/image-209.png)
4.Preparation of alkyl halides:
a)Alcohol when reacted with ZnCl2/HCl (Lucas Reagent), alkyl halide is produced.As alkyl halides are insoluble in water, turbidity is produced.
- 30 alcohol forms turbidity immediately
- 20 alcohol forms turbidity within 5 mins
- 10 alcohol forms turbidity shows no turbidity at room temperature.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 28 Preparation of alkyl halide from alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-210.png)
b) Alkyl halides can also be produced from alcohol by PCl5 or PCl3 or SOCl2 . Thionyl chloride is preferred as it produce two gaseous side products, which can be removed easily.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 29 Preparation of alkyl halide from alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-212.png)
5.Dehydration:
Alcohols when heated with conc.H2SO4 at 1700C alkene are produced by saytzeff’s rule.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 30 Preparation of alkene from alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-213.png)
6.Preparation of ethers:
Alcohols when heated with conc.H2SO4 at 1400C ethers are produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 31 Preparation of ethers from alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-214.png)
7.Oxidation:
- 10 alcohol when treated with Conc. H2SO4 /K2Cr2O7, carboxylic acid is produced. At first, aldehyde is produced, which further undergoes oxidation to produce carboxylic acid.
- 20 alcohol when treated with Conc. H2SO4 /K2Cr2O7, ketone is produced.
- 30 alcohol does not undergoe oxidation with Conc. H2SO4 /K2Cr2O7.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 32 Complete oxidation of alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-215.png)
- When Jones Reagent is used, primary alcohol is partially oxidised to aldehyde.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 33 Parial Oxidation of alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-216.png)
Test for alcohol
Victor Meyer’s Test
Reagent reactant is treated with Red P + I2, then AgNO2 then NaNO2 + dil H2SO4, then NaOH
- 10alcohol →Blood Red
- 20alcohol →Blue
- 30alcohol →Colourless.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 34 image 217 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-217.png)
Interconversion of alcohols
1.Conversion of Lower to higher alcohol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 35 Conversion of Lower to higher alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-218.png)
2.Conversion of Higher to Lower alcohol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 36 Conversion of Higher to Lower alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-219.png)
3.Conversion of Primary to secondary alcohol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 37 Conversion of Primary to secondary alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-220.png)
4.Conversion of Secondary to Tertiary alcohol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 38 Conversion of Secondary to Tertiary alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-221.png)
5. Conversion of Primary to Tertiary alcohol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 39 Conversion of Primary to Tertiary alcohol](https://www.allaboutchemistry.net/storage/2020/07/image-222.png)
Phenol
Preparation of Phenol
1.From Benzene
Benzene when reacted with fuming sulphuric acid, produce benzenesulphonic acid. Benzenesulphonic acid when heated with NaOH, sodium phenoxide is produced, which on acidic hydrolysis produce phenol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 40 Preparation of phenol from benzene](https://www.allaboutchemistry.net/storage/2020/07/image-223.png)
2.From Benzene diazonium chloride
Benzene diazonium chloride when treated with warm water, phenol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 41 image 224 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-224.png)
3.From chlorobenzene
Chlorobenzene when heated with sodium carbonate at 3000 C and 200 atm pressure in the presence of Catalyst, phenol is produced.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 42 Preparation of phenol from chlorobenzene](https://www.allaboutchemistry.net/storage/2020/07/image-225.png)
4.From Aniline
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 43 Preparation of phenol from aniline](https://www.allaboutchemistry.net/storage/2020/07/image-226.png)
5.From phenyl magnesium bromide
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 44 Preparation of phenol from phenyl magnesium bromide](https://www.allaboutchemistry.net/storage/2020/07/image-227.png)
6.From cumene
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 45 Preparation of Phenol from cumene](https://www.allaboutchemistry.net/storage/2020/07/image-228.png)
Reactions of Phenol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 46 Reactions of Phenol](https://www.allaboutchemistry.net/storage/2020/07/Phenol-Reactions-768x1024.jpg)
Acidity of phenol:
Phenoxide ions produced from phenol is more resonance stabilized than phenol. Thus phenol shows acidic property due to formation of H+ ion.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 47 image 229 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-229.png)
Resonance of phenol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 48 image 230 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-230.png)
Resonance in phenoxide ion
In case of alcohol, neither the alcohol nor the alkoxide ion is stabilized by resonance.
Thus, Phenol is stronger acid as compared to alcohol but weaker acid as compared to acetic acid.
- Effect of substitution on the acid strength of phenol:
- Electron withdrawing groups like –NO2, -CN, -X, -CHO stabilizes the phenoxide ion . Thus increases the acidic strength.
- The effect is more pronounced in o-p position than in m-position.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 49 image 231 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-231.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 50 image 232 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-232.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 51 image 233 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-233.png)
- –R, -OR, -NH2 decreases the acidic strength.m-cresol>p-cresol>o-cresol
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 52 image 234 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-234.png)
Extra Information
- Methylated spirit or Denatured alcohol: Rectified spirit (5 – 10%) + methanol + pyridine
- Absolute Alcohol: 100% alcohol
- Rectified spirit: 93 – 95% alcohol rest water
- Power alcohol: Alcohol + Benzene
- Surgical spirit: 95% rectified spirit + 5% methanol
- Alcoholometry: Determination of the strength of alcohol.
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 53 image 235 ALL ABOUT CHEMISTRY](https://www.allaboutchemistry.net/storage/2020/07/image-235.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 54 BHT](https://www.allaboutchemistry.net/storage/2020/07/image-238.png)
![Alcohol and Phenol|Class 12|ISC|CBSE|JEE|NEET 55 Detol](https://www.allaboutchemistry.net/storage/2020/07/image-239.png)
Important information
- The aqueous solution of phenol is called carbolic acid.
- Cresol<Phenol<p-Chlorophenol<m-nitrophenol<o-nitrophenol<p-nitrophenol<<picric acid(acidic )
- O<m<p (solubility of nitrophenols in water)
- Phenols cannot be converted directly to esters by reacting with carboxylic acids like alcohol. Because the esterification reaction is exothermic for alcohols but slightly endothermic for phenols. And phenols are less nucleophilic than alcohol.
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