Functional Class Nomenclature of Alcohols( Common Names) Name the alkyl group and add "alcohol" as a separate word. 4 CH 3 CH 2 OH CH 3 CH 2 OH CH 3 CHCH 2 CH 2 CH 2 CH 3 CH 3 CHCH 2 CH 2 CH 2 CH 3OH CH 3 CCH 2 CH 2 CH 3 OH CH 3 Ethyl alcohol Ethyl alcohol 1-Methylpentyl alcohol 1-Methylpentyl alcohol 1,1-Dimethylbutyl alcohol
IUPAC Nomenclature of Alcohols Name as "alkanols." Replace –e ending of alkane name by -ol. Number chain in direction that gives lowest number to the carbon that bears the —OH group. CH 3 CH 2 OH CH 3 CHCH 2 CH 2 CH 2 CH 3 OH CH 3 CCH 2 CH 2 CH 3 OH CH 3 Ethanol Ethanol 2-Hexanol 2-Hexanol 2-Methyl-2-pentanol
Name these: 6 2-methyl-1-propanol 2-methyl-2-propanol 2-butanol 3-bromo-3-methylcyclohexanol =>
Unsaturated Alcohols Number the chain in thedirection that gives the lowest number to the carbon that bears the OH group 7 4-penten-2-ol (old) pent-4-ene-2-ol =>
Hydroxy Substituent When -OH is part of a higher priority class of compound, it is named as hydroxy. Example: 9 4-hydroxybutanoic acid =>
Classes of Alcohols Primary: carbon with –OH is bonded to one other carbon. -CH2OH Secondary: carbon with –OH is bonded to two other carbons. -CHOH Tertiary: carbon with –OH is bonded to three other carbons. -COH => 10
Diols Two numbers are needed to locate the two -OH groups. Use -diol as suffix instead of -ol. Chapter 1013 1,6-hexanediol =>
Glycols 1, 2 diols (vicinal diols) are called glycols. Common names for glycols use the name of the alkene from which they were made. 14 1,2-ethanediol ethylene glycol 1,2-propanediol propylene glycol =>
Thiols Contains an –SH (sulfhydryl) group. Is named by selecting the longest carbon chain that contain the -SH. We add -thiol to the name of the parent alkane. Parent chain is numbered from the end nearest tothe -SH group. Methanethiol Ethanethiol CH 3 ─ S ─ HCH 3 ─ CH 2 ─ S ─ H
Physical Properties of Alcohols 1.Alcohols are polar molecules (because of O-H and C- O). 2. Have higher boiling point than Alkanes, Alkenes & Alkynes due to Hydrogen bonding involves oxygen of one molecule and hydrogen of another in alcohol molecules. 3. As the molecular weight increase, boiling point decrease. 4.As the molecular weight increase, solubility in water decrease. 5.The solubility of alcohols in water is due to hydrogen bonding between alcohol and water molecules. 6. They are weak acids (weaker than Phenol).
PHYSICAL PROPERTIES OF ALCOHOLS, cont. The –OH group can hydrogen bond between alcohol molecules leading to relatively high boiling points. Hydrogen bonding in pure ethanol:
PHYSICAL PROPERTIES OF ALCOHOLS The –OH group is polar and capable of hydrogen bonding. This makes low molecular weight alcohols highly soluble in water. Hydrogen bonding in a water-methanol solution:
Acidity of Alcohols pK a range: 15.5-18.0 (water: 15.7) Acidity decreases as alkyl group increases. Halogens increase the acidity. Phenol is 100 million times more acidic than cyclohexanol! => Chapter 1021
Preparation of Alcohols by Hydration of Alkenes Water molecule add to double bond in accordance with Markovnikov’s rule
Preparation of Alcohols by Grignard Reagents By reaction of grignard reagents with aldehydes and ketones to form Primary, Secondary and Tertialy Alcohols.