1. ALCOHOLS
340 Chem 1st 1439

2. Learning Objectives By the end of this chapter the student will:
know the structure of alcohol
Knew the different classes of alcohols.
Knew the nomenclature of Alcohols
Knew the physical Properties.
Knew the acidity of Alcohols.
Knew the different methods of preparation of Alcohols .
Knew the chemical reactions of Alcohols
340 Chem 1st 1439

3. Alcohols Structural Characteristic of Alcohols
alcohols, a class of compounds containing the OH (hydroxyl) group.
Alcohols have a hydroxyl ( OH) group bonded to a saturated carbon atom. The alcohol carbon atom may be part of a simple alkyl group, an alkenyl or alkynyl group, or the carbon atom may be a saturated carbon atom that is attached to a benzene ring:
340 Chem 1st 1439

4. Classification of Alcohols
Alcohols are classified as primary, secondary, or tertiary according to the classification of the carbon that bears the functional group.
The carbon atom which connected to the hydroxyl group called carbinol carbon.
340 Chem 1st 1439

5. 340 Chem 1st 1439

6. Nomenclature of Alcohols
In the IUPAC system: selected the longest carbon chain that contains the -OH group as the parent alkane and numbered from the end closer to OH. change the suffix -e of the parent alkane to -ol
use a number to show the location of the OH group.
If there is a functional group suffix and a substituent, the functional group suffix gets the lowest possible number.
For cyclic alcohols, numbering begins with the carbon bearing the OH group. If the OH group is understood to be on carbon 1 of the ring.
In complex alcohols, the number for the hydroxyl group is often placed between the infix and the suffix. So the compound containing two hydroxyl groups is named as a diol, one containing three hydroxyl groups as a triol, and so on.
340 Chem 1st 1439

7. Compounds containing OH and C=C groups are often referred to as unsaturated alcohols. choose the chain that include them both even if this is not the longest chain.
In the IUPAC system, the double bond is shown by changing the infix of the parent alkane from -an- to -en- and the hydroxyl group is shown by changing the suffix of the parent alkane from -e to -ol.
Numbers must be used to show the location of both the carbon-carbon double bond and the hydroxyl group.
Common names derived by naming the alkyl group followed by the word alcohol.
340 Chem 1st 1439

8. Alcohol functional group suffix is ol CH3OH methanol Common Name
Note
IUPAC Name
Alcohol functional group suffix is ol
CH3OH methanol
Common Name
alkyl group attached to OH, plus alcohol
CH3OH methyl alcohol
340 Chem 1st 1439

9. Chair Conformations
340 Chem 1st 1439

10. Physical Properties of Alcohols
Most of the common alcohols, up to about 11 or 12 carbon atoms, are liquids at room temperature. Methanol and ethanol are free-flowing volatile liquids with characteristic fruity odors. The higher alcohols (the butanols through the decanols) are somewhat viscous, and some of the highly branched isomers are solids at room temperature. These higher alcohols have heavier but still fruity odors.
Solubility
Water and alcohols have similar properties because they all contain hydroxyl groups that can form hydrogen bonds.
Several of the lower-molecular-weight alcohols as CH3OH,,,,C3H7OH are miscible (soluble in any proportions) with water.
The solubility decreases as the alkyl group becomes larger.
The number of hydroxyl groups increases so the solubility increases.
340 Chem 1st 1439

11. Boiling Points
Alcohols have much higher boiling points than comparable ethers or hydrocarbons.
Alcohol molecules can associate with each other through hydrogen bonding, whereas those of ethers and hydrocarbons cannot.
The boiling points increase with the increase of the number of OH groups .
the boiling point decreases with increase in branching
in the alkyl group.
Boiling points of 1o alcohol > 2o alcohol > 3o alcohol
340 Chem 1st 1439

12. 340 Chem 1st 1439

13. Acidity of Alcohols
Alcohols can function as both weak acids (proton donors) and weak bases (proton
acceptors).A strong base can remove the hydroxyl proton to give an alkoxide ion.
Alkoxide ions are strong nucleophiles and strong bases
The order of acidity of various liquid alcohols generally is water > 1o>2o>3o
Electron-withdrawing groups make an alcohol a stronger acid by stabilizing the conjugate base (alkoxide)
The acidity decreases as the substitution on the alkyl group increases, because a more highly substituted alkyl group inhibits solvation of the alkoxide ion, decreasing the stability of the alkoxide ion and driving the dissociation equilibrium toward the left.
Alcohol weaker acids than phenol and carboxylic acids
The basicity of alkoxide ions increases while going from primary to tertiary. This increase in basicity occurs because the conjugate base of a weak acid is strong.
340 Chem 1st 1439

14. The common name of an alkoxide is constructed by deleting the final yl from the name of the alkyl group and adding the suffix oxide. In substitutive nomenclature, the suffix ate is simply added to the name of the alcohol.
340 Chem 1st 1439

15. Synthesis of Alcohols 1-Synthesis of Alcohols from alkenes
a- By acid catalysed hydration in accordance with Markownikoff’s rule.
b-Anti-Markovnikov’s rule, ( Hydroboration-Oxidation)
C- Dihydroxylation: synthesis of 1,2-diols from alkenes
340 Chem 1st 1439

16. 2-Hydrolysis of alkyl halides
340 Chem 1st 1439

17. 3-Reaction of Grignard reagents with aldehydes , ketones, esters and epoxides
340 Chem 1st 1439

18. Ester or acid chloride ( CH3COOCH3 or CH3COCl)
Epoxide
340 Chem 1st 1439

19. 4-Reduction of Aldehydes, Ketones, Acids and Esters
by hydrogenation of the carbon–oxygen double bond.
sodium borohydride (NaBH4) reduce carbonyl groups
lithium aluminum hydride (LiAlH4) reduce all kind of carbonyl groups
H2/ Ni or Pt or Pd or Ru reduce all double bond
340 Chem 1st 1439

20. 340 Chem 1st 1439

21. Reactions of Alcohols I
Reactions of Alcohols I.Reaction as acids (Breaking of oxygen- Hydrogen bond CO ـــــH)
A. Formation of Salt (Na, K, Mg)
B. Formation of Esters (Carboxylic acid ester)
340 Chem 1st 1439

22. II. Reaction involving carbon-oxygen bond cleavage C-OH Conversion of Alcohols into Alkyl Halides
The order of reactivity of alcohols is 3°> 2° >1° > methyl.
By using Hydrogen halides (HCl, HBr, Hl) or Phosphorus tribromide (PBr3) or Thionyl chloride (SOCl2)
340 Chem 1st 1439

23. Elimination Reactions(Dehydration of alcohols)
1. Formation of alkenes
2. Ethers Formation
340 Chem 1st 1439

24. Oxidation of Alcohols to Carbonyl Compounds
Cu/ Heat or CrO3/ Pyridine or PCC/CH2Cl2 (weak)
(STRONG):KMnO4, K2Cr2O7/H3O+ , H2Cr2O7/H3O+, HNO3
Tertiary alcohols have no hydrogen on their hydroxyl-bearing carbon and do not undergo oxidation readily
340 Chem 1st 1439