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Alcohols and Phenols and how to identify them Classification • Primary: carbon with –OH is bonded to one other carbon • Secondary: carbon with –OH is bonded to two other carbons • Tertiary: carbon with –OH is bonded to three other carbons • Aromatic (phenol): -OH is bonded to a benzene ring 2 Classify these: CH3 CH3 CH3 CH CH2OH CH3 C OH CH3 OH OH CH3 CH CH2CH3 3 IUPAC Nomenclature • Find the longest carbon chain containing the carbon with the -OH group • Drop the -e from the alkane name, add –ol • Number the chain, starting from the end closest to the -OH group • Number and name all substituents. => 4 Name these: CH3 CH3 CH CH2OH 2-methyl-1-propanol OH CH3 CH CH2CH3 2-butanol CH3 CH3 OH C OH CH3 2-methyl-2-propanol Br CH3 3-bromo-3-methylcyclohexanol => Chapter 10 5 Naming Phenols • -OH group is assumed to be on carbon 1 • For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para- for 1,4 • Methyl phenols are cresols. OH Cl 3-chlorophenol meta-chlorophenol OH H3C 4-methylphenol para-cresol 6 Physical Properties • Unusually high boiling points due to hydrogen bonding between molecules • Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases. 7 Acidity of Phenol • In water, phenol acts as a weak acid phenol phenoxide ion Oxidation of Alcohols: Do I have a tertiary alcohol? • • • For Primary alcohols that dehydrogenate from the aldehyde to the carboxylic acid tertiary alcohols do not dehydrogenate (oxidize) Secondary alcohols only oxidize to the ketone + Cr3+ + Cr3+ If chromic acid is used for H2CrO4=[O] then the product includes Cr3+ which is green 9 Oxidation with Chromate Negative test tertiary alcohol Positive test primary or secondary alcohol Test of a Phenol: FeCl3 test • You can test for a phenol with ferric chloride (FeCl3) Phenol + Fe3+ [Fe3+.phenol complex] colorless yellow purple Experiment You will test the following • ethanol • 2-propanol • 2-methyl-2-propanol • Cyclohexanol • Phenol • Unknown Experiment • • • • • • Odor Solubility in water Acidity Reaction with Chromic Acid Ferric Chloride Test Use test results to identify your unknown