Alcohols, Ethers and Thiols

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Chapter 14

• Alcohols, Ethers and Thiols

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Derivatives of Water

• Alcohols, ROH
• Ethers, ROR
• Thiols, RSH

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Nomenclature
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Classification by Carbon Degree
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• Methyl alcohol primary alcohol
• Ethyl alcohol primary alcohol
• n-propyl alcohol primary alcohol
• isopropyl alcohol secondary alcohol

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• n-butyl alcohol primary alcohol
• sec-butyl alcohol secondary alcohol
• isobutyl alcohol primary alcohol
• tert-butyl alcohol tertiary alcohol

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Common Alcohols

• Methyl alcohol wood alcohol
• metabolism produces formaldehyde
• causes blindness
• used as fuel in racing cars (dangerous,
  invisible flames)

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Common Alcohols

• Ethyl alcohol grain alcohol
• distillation to produce gt 10 12
• Isopropyl alcohol rubbing alcohol
• Ethylene glycol antifreeze
• hazard to pets
• Glycerol (glycerine) backbone of lipids

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Physical Properties

• R-OH
• Capable of hydrogen bonding
• Higher bp than comparable MW alkanes
• More soluble than comparable MW alkanes
• polar soluble to C4
• C to O ratio lt 41 means soluble
• diols are more soluble
• triols are even more soluble
• glucose has 5 OH groups

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Question

• Which has the higher boiling point?
• 1-propanol or butane

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Chemical Properties

• 1. Combustion
• alcohol O2 ? CO2 H2O

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• 2. Elimination (dehydration)
• alcohol ? alkene water
• Tsayseffs rule
• the poor get poorer
• 2-butanol ? 2-butene H2O

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• 3. Oxidation Reduction Reactions
• Definitions
• oxidation gain of oxygen or loss of hydrogen
• reduction gain of hydrogen or loss of oxygen

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• Primary alcohol
• ethyl alcohol ?
• acetaldehyde ?
• acetic acid

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• Secondary alcohol
• isopropyl alcohol ?
• acetone

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• Tertiary alcohol
• tert-butyl alcohol ?
• no reaction

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Examples

• O oxidation
• H reduction

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Acidity of alcohols and phenols

• CH3OH HCl ? NR
• CH3OH NaOH ? NR
• (must have base stronger than OH)
• Phenol NaOH ? phenylate ion
• Na H2O

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Ethers Nomenclature

• Name alkyl groups alphabetically
• dimethyl ether
• diethyl ether
• isobutyl sec-butyl ether

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Physical Properties

• No hydrogen bonding
• lower bp than alcohols
• less soluble than alcohols
• Boiling points
• alkanes lt ethers lt alcohols
• Solubility
• alkanes lt ethers lt alcohols
• ltdiols lt triols

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Chemical Properties

• Combustion
• Peroxide formation
• R-O-R can be oxidized to R-O-O-R
• R-O-O-R can be reduced to R-O-R
• H-O-O-H hydrogen peroxide

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Thiols Nomenclature

• CH3SH methyl mercaptan
• methanethiol
• CH3CH2SH ethyl mercaptan
• ethanethiol

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Physical Properties

• Characteristic odors
• skunk
• onion

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Chemical Properties

• Redox
• Thiols can be oxidized to disulfides
• 2R-SH ? R-S-S-R
• Disulfides can be reduced to thiols
• R-S-S-R ? 2R-SH