organic chemistry for 10th graders

1. ALCOHOLS , PHENOLS AND
ETHERS
-renuha

2. The alcohol is given priority over
the double bond.
PHENOL IS NOT AN ALCOHOL
Cresol: methylphenol

3. The bond angle in alcohols is slightly less than the tetrahedral angle as In alcohols, the oxygen of –OH
group is attached to sp3 hybridized carbon atom and there is repulsion between the unshared electron pairs of
oxygen.
In phenols , the bond length is slightly lesser than that of methanol due to (i)partial double bond character
formation due to unshared electron pair of oxygen and (ii)the oxygen is connected to a sp2 carbon.
In ethers, the four electron pairs, i.e., the two bond pairs and two lone pairs of electrons on oxygen are
arranged 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
Phenol does not undergo nucleophilic substitution reaction easily due to:
partial double bond character of C-OH bond

4. Preparation of Alcohol
1.Alcohols from alkenes:
i)HYDRATION-- addition reaction
follows MARKOVNIKOV'S RULE [the poorer carbon becomes even poor when the OH group attaches itself to it.]
Takes place in the presence of an ACID [H2SO4]
MECHANISM:
Step I → Protonation of alkene to form carbocation
Step II→ nucleophilic attack
Step III→ Deprotonation to form alcohol
ii)Hydroboration-oxidation : follows ANTI-MARKOVNIKOV'S RULE [Richer carbon gets the OH group]
-Takes place in the presence of hydrogen peroxide

5. 2.Alcohols from carbonyls: [reduction reaction]
Aldehydes and ketones are reduced to alcohols by adding hydrogen to them in the presence of a catalyst.
CATALYSTS:
i)hydrogen in palladium or nickel or platinum
ii)LiAlH4
[strong reducing agent but is very expensive][used to prepare only special chemicals]
iii) NaBH4
● Carboxylic acid is reduced to primary alcohols in excellent yields by lithium aluminium hydride, a strong
reducing agent
Commercially acids are reduced to alcohols by converting them into ESTERS and then hydrogenation to form
alcohols.
Aldehydes → PRIMARY ALCOHOL
Ketones → SECONDARY ALCOHOL

6. 3. Alcohols from grignard reagent :
Grignard reagent + aldehyde or ketone [in the presence of h2o ] → alcohol +MgOH(X)
Step I : nucleophilic addition of grignard reagent to carbonyl group , forms adduct
Step II : hydrolysis of adduct -->alcohol
R-Mg-X : bond between R and Mg is a covalent bond while bond between Mg and X is an ionic bond
Methanal in grignard → primary alcohol
Aldehyde in the presence of grignard → secondary alcohol
Ketone in the presence of grignard → tertiary alcohol

7. Preparation of phenols
1.Dow’s process:[from haloarenes] 2. From benzene sulphonic acid:
3.diazonium salts:
4. From cumene
Most of the worldwide production of phenol is from
cumene.

8. Physical properties of Alcohols
1.Boiling points : increase with increase in no.of carbon atoms [as the van der waals force increases]
Decreases with increase in branching [as the surface area of the compound decreases and van der waals
forces also decrease]
1°>2°>3°
Alcohols have intermolecular hydrogen bonding making them stronger than alkyl halides and hydrocarbons
and increasing the their boiling points
2.Solubility : they are soluble in water as they can form hydrogen bonds with the water molecules
Larger the compound , lesser is the solubility
Lower molecular mass alcohols dissolve in water of all propotions
Alcohols and phenols are bronsted acids: can donate protons to a stronger base
Alcohols are weaker acids than water
Alcohols act as Bronsted bases as well. It is due to the presence of unshared electron pairs on oxygen, which makes them

9. -More the degree less is the acidity:
As there are more electron releasing groups , the electron density increases decreasing the o-h polarity which
decreases the acidity of the alcohol.
Therefore , 1>2>3 [3° is the least acidic]
-phenols are more acidic than alcohols as:
--The phenoxide ion gets stabilised due to resonance
--The hybridisation is sp2 → more S character , more is the acidity
NOTE: nitro phenol is a more acidic group than phenol as nitro is an electron withdrawing group and it stabilses the
phenoxide ion and makes it more acidic
But cresol is less acidic than phenol as the ch3 group is an electron releasing group , which destabilises the
compound and makes it less acidic.
Phenol molecule is less stable than phenoxide ion

10. Alcohols react as both electrophiles and nucleophiles.
If o-h is broken then it acts as a nucleophile , if c-o is broken , acts as an electophile.

11. ESTERIFICATION
Phenol or alcohol + carboxylic acid or acid anhydride [presence of conc h2so4]→ ester
A reversible reaction
Or
Phenol or acohol +acid halide [pyridin(base {neutralises the HCl formed during the reaction and always
keeps the reaction moving forward})] → ester
Introduction of acetyl to phenol or alcohol is called acetylation
-acetylation of salicylix acid gives asprin:
Salicylic acid +(ch3co)2o [acetyl] → aspirin
Aspirin is also called as acetylsalicylic acid.
Order of esterification of alcohols are:1 ° > 2° > 3°

12. Dehydration
Alcohols undergo dehydration (removal of a molecule of water) to form alkenes on treating with a protic
acid
protic acids (H2SO4, H3PO4). The formation of the reaction product, alkene or ether depends on the
reaction conditions
Good dehydrating agents:
1. Conc H2SO4 [strong]
2. H3PO4
3. Anhydrous zncl2 [catalyst]
4. Al2o3 [catalyst]
3°>2°>1° [3 is most prone to dehydration , therefore requires only mild agents (1° requires strong agent)]

13. Luxas reagent

14. Oxidation
Alcohol → carbonyls→ carboxylic acid [on oxidation]
Carboxylic → carbonyls → alcohol [on reduction]
Alcohol → carboxylic [on STRONG OXIDATION]
Oxidising agents:
Mild: cro3 , cro3 in ch3cooh , pcc [pyridinium chloro cromate] {converts alcohol to carbonyls},
Strong: acidified and alkaline KMnO4 and k2cr2o7 , conc hno3 , cro3 in h2so4 [jones reagent] ,
Strong reagents convert alcohols to carboxylic acid straight
Tertiary alcohols dont undergo oxidation

15. dehydrogenation
When the vapours of a primary or a secondary alcohol are passed over heated copper at 573 K,
dehydrogenation takes place and an aldehyde or a ketone is formed
tertiary alcohols undergo dehydration and produce an alkene.
1. cu/ag/au at 573k

16. PHENOL and its reactions [electrophilic subs]
1.Nitration [dil nitric acid(low temp) →nitrophenol]
2.Halogenation
3.Kolbe’s reaction [naoh , co2 , salicylic acid/Ortho hydroxybenzoic acid] {electrophilic aromatic substitution.}
4.reimen teimen’s reaction [phenol with CHCl3 and aqueous NaOH at 343 K, the electrophile attacking the ring is:
ccl2 , salicaldehyde]
5.phenol with zinc dust [gives benzene]
6.oxidation [phenol +chromic acid →[diketone ]benzoquinone , in air phenols oxidised to dark coloured mixtures
containing quinones.]
NOTE :OH group is a hughly activating group

17. Ortho and para can be SEPERATED by STEAM DISTILLATION.
Ortho is steam volatile due to INTRAMOLECULAR hydrogen bonding and therefore distils out first
But PARA has INTERMOLECULAR hydrogen bonding and comes out laetr.
NITRATION:
If conc hno3 is used then 2,4,6-trinitrophenol is formed

18. halogenation
Case 1.br in solvents of low polarity such as CHCl3 or CS2 low temperature → o-bromophenol and
p-bromophenol
Case 2.phenol with bromine water,2,4,6-tribromophenol is formed as white precipitate

19. Kolbe’s reaction
● Phenol with sodium hydroxide gives a phenoxide ion [even more reactive than phenol towards
electrophilic substitution]
● Therefore once again undergoes electrophilic substitution reaction in the presence of CO2 a weak
electrophile
● Ortho hydroxybenzoic acid/salicylic acid is formed as the main reaction product.

21. ethers
Dehydration reaction:
The formation of ether is a nucleophilic bimolecular reaction (SN2) involving the attack of alcohol molecule on a
protonated alcohol.;
The method is suitable for the preparation of ethers having primary alkyl groups only. The alkyl group should be
unhindered and the temperature be kept low.
But reaction follows SN1 pathway if the alcohol is secondary or tertiary

22. Williamson synthesis
-It is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers.
-an alkyl halide is to react with sodium alkoxide to give ether
-Ethers containing substituted alkyl groups (secondary or tertiary) may also be prepared by this method.
-The reaction involves SN2 attack of an alkoxide ion on primary alkyl halide.
-Better results are obtained if the alkyl halide is primary. In case of secondary and tertiary alkyl halides,
elimination competes over substitution. If a tertiary alkyl halide is used, an alkene is the only reaction product and
no ether is formed
Sn2 reaction is used

23. Physical properties
Highly volatile and inflammable
The C-O bonds in ethers are polar and thus, ethers have a net dipole moment.
BOILING POINT
The weak polarity of ethers do not affect their boiling points.
Alcohols have more boiling point than ethers due to due to the presence of stronger hydrogen bonding in alcohols.
SOLUBILITY:
Soluble in water
This is due to the fact that just like alcohols, oxygen of ether can also form hydrogen bonds with water molecule

25. Very slightly reactive , almost inert , due t oabsense of polarity beteen c-o bond

26. Ether follows sn2 where alcohol is protonated with a proton from h2so4
Ethers are basic
Dehydration of alcohols gives primary ether
Williamson synthesis : can prepare 1 , 2 , 3 degrees ether [nucleophilic sub]
Halide alkoxide→ ester
Only 1 degree alcohol is used in this process as 2 or 3 gives an alkene

27. Extra questions
1.Picric acid is a yellow coloured compound. Its chemical name is: 2, 4, 6-trinitropheriol
2.Phenol when treated with excess of bromine water gives a white precipitate of:2, 4, 6-tribromophenol
3.Ortho-nitrophenol is less soluble in water than, p- and m- nitrophenols because: o-nitrophenol shows
intramolecular H-bonding
4.The reaction between phenol and chloroform in the presence of aqueous NaOH is electrophilic substitution
reaction
5.The major product obtained on interaction of phenol with sodium hydroxide and carbon dioxide is:salicylic
acid

28. MCQ SITES
1. LINK 1
2. LINK 2
3. LINK 3
4. NOTES