1. Physical and Chemical Properties Of Alcohols!
BY GHULAM ABBAS

2. Introduction Primary Alcohol:
Alcohol is any compound in which a hydroxyl functional group (-OH) is bound to a carbon atom.
There are three classes (types) of alcohols:
primary
secondary
and tertiary
Primary Alcohol:
In a primary (1°) alcohol, the carbon which carries the -OH group is only attached to one alkyl group.
General formula: RCH2OH

3. Secondary Alcohol: Tertiary Alcohol: Primary Alcohol examples
Methanol Ethanol
Secondary Alcohol:
In a secondary (2°) alcohol, the carbon with the -OH group attached is joined directly to two alkyl groups.
General formula: R2CHOH
Tertiary Alcohol:
In a tertiary (3°) alcohol, the carbon atom holding the -OH group is attached directly to three alkyl groups.
General formula: R3COH

4. Physical Properties of Alcohol
Molecular state:
straight chain alcohols with up to 12 carbon atoms are liquids.
Solubility:
alcohols with a small organic part as methanol or ethanol are much like water, thus miscible with water.
Alcohols with a larger molecular weight are more like alkane and less like water.
Alcohols with more than two -OH groups are more water soluble than similar alcohols with only one -OH group.

5. Physical Properties of Alcohol
In general each -OH group can solubilize four to five carbon atoms.
For example: Glycerol
Boiling point:
the boiling point of an alcohol is always much higher than that of the alkane with the same number of carbon atoms.
alcohols with two or more –OH groups have higher boiling point.

6. Physical Properties of Alcohol
Methanol, Ethanol and Glycerol:
Color
colorless
Odor
they have faint odor (alcoholic odor) except glycerol which is odorless.
Solubility
completely miscible with water.
Flammability
flammable with blue, non smoky flame.
State
liquid except glycerol which is viscous liquid.
Acid-base properties
neutral

7. Chemical Properties of Alcohol
Oxidation:
The oxidising agent used is a solution of potassium dichromate (K2Cr2O7) acidified with sulphuric acid (H2SO4).
If oxidation occurs, the orange solution containing the dichromate ions is reduced to a green solution containing chromium ions.

8. Reactions of Alcohols
Conversion of alcohols into alkyl halides:
3˚ alcohols react with HCl or HBr by SN1 through carbocation intermediate
1˚ and 2˚ alcohols converted into halides by treatment with SOCl2 or PBr3 via SN2 mechanism

9. Reactions of 1˚ and 2˚ alcohols

10. Dehydration of Alcohols to Yield Alkenes
The general reaction: forming an alkene from an alcohol through loss of O-H and H (hence dehydration) of the neighboring C–H to give  bond
Specific reagents are needed

11. Acid- Catalyzed Dehydration
Tertiary alcohols are readily dehydrated with acid
Secondary alcohols require severe conditions (75% H2SO4, 100°C) - sensitive molecules do not survive
Primary alcohols require very harsh conditions – impractical
Reactivity is the result of the nature of the carbocation intermediate

12. Incorporation of Alcohols into Esters

13. Oxidation of Alcohols
Can be accomplished by inorganic reagents, such as KMnO4, CrO3, and Na2Cr2O7 or by more selective, expensive reagents

14. Mechanism of Chromic Acid Oxidation
Alcohol forms a chromate ester followed by elimination with electron transfer to give ketone
The mechanism was determined by observing the effects of isotopes on rates

15. Aldehydes and Ketones

16. Introduction Aldehydes are compounds of the general formula RCHO;
Ketones are compounds of the general formula RR´CO. The groups R and R´ may be aliphatic or aromatic.
Both aldehydes and ketones contain the carbonyl group, C=O, and are often called carbonyl compounds.

17. An aldehyde is often written as RCHO
An aldehyde is often written as RCHO. Remember that the H atom is bonded to the carbon atom, not the oxygen.
Likewise, a ketone is written as RCOR, or if both alkyl groups are the same, R2CO.
The three bonds (carbon, oxygen, and the two other atoms attached to carbonyl carbon) lie in a plane; the three bond angels of carbon are very close to 120º.

18. Nomenclature Naming Aldehydes in the IUPAC System
Both IUPAC and common names are used for aldehydes and ketones.
Naming Aldehydes in the IUPAC System
To name an aldehyde using the IUPAC system:
[1] If the CHO is bonded to a chain of carbons, find the longest chain containing the CHO group, and change the -e ending of the parent alkane to the suffix -al.
If the CHO group is bonded to a ring, name the ring and add the suffix -carbaldehyde.
[2] Number the chain or ring to put the CHO group at C1

19. Give the IUPAC name for the compounds:

20. Naming Ketones in the IUPAC System
To name an acyclic ketone using IUPAC rules:
[1] Find the longest chain containing the carbonyl group, and change the -e ending of the parent alkane to the suffix -one.
[2] Number the carbon chain to give the carbonyl carbon the lower number. Apply all of the other usual rules of nomenclature.

23. Physical properties: Boiling point:
Aldehydes and ketones are polar compounds due to the polarity of carbonyl group and hence they have higher boiling points than non polar compounds of comparable molecular weight.
But they have lower boiling points than comparable alcohols or carboxylic acids due to the intermolecular hydrogen bonding.

24. Solubility:
The lower aldehydes and ketones soluble in water, because of hydrogen bonding between carbonyl group and water, also they soluble in organic solvents.

25. Reactions of Aldehydes and Ketones
Aldehydes and Ketones undergo many reactions to give a wide variety of useful derivatives. There are two general kinds of reactions that aldehydes and ketones undergo:
[1] Reaction at the carbonyl carbon (Nucleophilic addition reactions).

26. [2] Reaction at the α carbon
A second general reaction of aldehydes and ketones involves reaction at the α carbon. A C–H bond on the α carbon to a carbonyl group is more acidic than many other C–H bonds, because reaction with base forms a resonance-stabilized enolate anion.

27. Acid-catalyzed nucleophilic addition
The general mechanism for this reaction consists of three steps (not two), but the same product results because H and Nu- add across the carbonyl π bond. In this mechanism protonation precedes nucleophilic attack.
Step [1] Protonation of the carbonyl group

28. In Step [2], the nucleophile attacks, and then deprotonation forms the neutral addition product in Step [3].
Steps [2]–[3] Nucleophilic attack and deprotonation

29. a) Addition of Alcohols (Acetal Formation):
Aldehydes and ketones react with two equivalents of alcohol to form acetals. In an acetal, the carbonyl carbon from the aldehyde or ketone is now singly bonded to two OR" (alkoxy) groups.

30. b) Nucleophilic Addition of H- (Reduction reaction)
Treatment of an aldehyde or ketone with either Sodium borohydride (NaBH4) or Lithium hydride (LiAlH4) followed by protonation forms a 1° or 2° alcohol.

31. Hydride reduction of aldehydes and ketones occurs via the two-step mechanism of nucleophilic addition, that is, nucleophilic attack of H:– followed by protonation.

32. c) Reduction to alkane (Deoxygenation of Ketones and Aldehydes):
i) Clemmensen reduction.
ii) Wolff–Kishner reduction.

33. d) Nucleophilic Addition of CN– :
Treatment of an aldehyde or ketone with NaCN and a strong acid such as HCl adds the elements of HCN across the carbon–oxygen π bond, forming a cyanohydrin.

34. Carboxylic Acids Structure
Carboxylic acid groups consist of two very polar functional groups
Carbonyl group
Hydroxyl group
Carboxylic acid groups are very polar

35. Physical Properties Low molecular weight carboxylic acids
Sharp, sour taste
Unpleasant aromas
High molecular weight carboxylic acids
Fatty acids important in biochemistry
Low molecular weight carboxylic acids are water soluble due to hydrogen bonding with:
Water
Each other

36. Physical Properties
Carboxylic acids exhibit dipole-dipole interactions because they have polar C—O and O—H bonds.
They also exhibit intermolecular hydrogen bonding.
Carboxylic acids often exist as dimers held together by two intermolecular hydrogen bonds.
Two molecules of acetic acid
(CH3COOH) held together by
two hydrogen bonds 36

37. Physical Properties
Due to carboxylic acids forming intermolecular hydrogen bonds boiling points are at higher temperatures than those of any other functional group studied

38. Nomenclature—The IUPAC System
In the IUPAC system, carboxylic acids are identified by a suffix added to the parent name of the longest chain with different endings being used depending on whether the carboxy group is bonded to a chain or a ring.
If the COOH is bonded to a chain, find the longest chain containing the COOH, and change the “e” ending of the parent alkane to the suffix “oic acid”.
If the COOH is bonded to a ring, name the ring and add the words “carboxylic acid”.
Number the carbon chain or ring to put the COOH group at C1, but omit this number from the name.
Apply all the other usual rules of nomenclature. 38

39. Compounds containing two carboxy groups are called diacids
Compounds containing two carboxy groups are called diacids. Diacids are named using the suffix –dioic acid.
Metal salts of carboxylate anions are formed from carboxylic acids in many reactions. To name the metal salt of a carboxylate anion, put three parts together: 39

40. Reactions of Carboxylic Acids
The most important reactive feature of a carboxylic acid is its polar O—H bond, which is readily cleaved with base. 40

41. The non-bonded electron pairs on oxygen create electron-rich sites that can be protonated by strong acids (H—A).
Protonation occurs at the carbonyl oxygen because the resulting conjugate acid is resonance stabilized (Possibility [1]).
The product of protonation at the OH group (Possibility [2]) cannot be resonance stabilized. 41

42. The polar C—O bonds make the carboxy carbon electrophilic
The polar C—O bonds make the carboxy carbon electrophilic. Thus, carboxylic acids react with nucleophiles.
Nucleophilic attack occurs at an sp2 hybridized carbon atom, so it results in the cleavage of the  bond as well. 42

43. Carboxylic Acids—Strong Organic BrØnsted-Lowry Acids
Carboxylic acids are strong organic acids, and as such, readily react with BrØnsted-Lowry bases to form carboxylate anions.

44. An acid can be deprotonated by a base that has a conjugate acid with a higher pKa.
Because the pKa values of many carboxylic acids are ~5, bases that have conjugate acids with pKa values higher than 5 are strong enough to deprotonate them. 44

45. 45

46. Carboxylic acids are relatively strong acids because deprotonation forms a resonance-stabilized conjugate base—a carboxylate anion.
The acetate anion has two C—O bonds of equal length (1.27 Å) and intermediate between the length of a C—O single bond (1.36 Å) and C=O (1.21 Å). 46

47. Resonance stabilization accounts for why carboxylic acids are more acidic than other compounds with O—H bonds—namely alcohols and phenols.
To understand the relative acidity of ethanol, phenol and acetic acid, we must compare the stability of their conjugate bases and use the following rule:
- Anything that stabilizes a conjugate base A:¯ makes the starting acid H—A more acidic. 47