Chapter 08 Alcohols, Ethers, and Thiols

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1 Alcohols, Ethers and Thiols Chapter 08 Alcohols, Ethers, and Thiols CEM 240: Fall 2016 Prof. Greg Cook 2 Alcohol Nomenclature - common imple alcohols are often named using common naming (functional class) considering the alkyl group as a substituent on the functional group. C 3 methyl alcohol C 3 C 2 ethyl alcohol a primary alcohol cyclopentyl alcohol a secondary alcohol Alcohol Nomenclature IUPAC naming is best using the carbon chain as the parent and replacing the -e ending with -ol note: alcohols outrank alkyl substituents 3 C methanol cyclopentanol propan-2-ol isopropyl alcohol a secondary alcohol t-butyl alcohol a tertiary alcohol 5-methylhexan-3-ol hexane-2,4-diol phenol N 2 o-nitrophenol 3 4 Properties of Alcohol Alcohols are polar but have other reactive features µ = 1.7 D weakly basic weakly acidic 5 ydrogen Bonding At about 5 kcal/mol, -bonds are weaker than covalent bonds but stronger than many other intermolecular forces δ hydrogen bond δ + δ δ + hydrogen bond δ + δ 6

2 Alcohol olubility Alcohols are similar to water but the solubility decreases as the hydrocarbon chain increases Alcohol C 3 C 3 C 2 Carbons 1 2 olubility in Water (g/100 g 2 ) Alcohol acid/base reactions Alcohols, like water, can be acids or bases weakly basic weakly acidic µ = 1.7 D alcohol + X acid + oxonium X alcohol + + water alkoxide hydronium 10 insoluble 7 8 Alcohol Acidity Preparation of Alkoxides C 3 C 2 + Na C 3 C 2 Na + 2 C 3 + Na C 3 Na Na Na Preparation of Alkyl alides from alcohols by a substitution reaction + X X + Alkyl Alcohol ydrogen alide Alkyl alide Water ynthesis of Alcohols - from alkenes 2 4 cat. + 2 F < Cl < < I reactivity C < < C < C < C methyl primary secondary tertiary reactivity 11 12

3 Preparation of Alkyl alides 120 C Preparation of Alkyl alides Can use a combination of halide salt and other ønsted acids Na 2 4 heat C 25 C Preparation of Alkyl alides Primary and secondary halides are best made by other means + Cl 2 Cl Cl eactions of Alcohols - Dehydration 2 4 cat P P eactions of Alcohols - xidation oxidation C C 1 alcohol aldehyde oxidation C carboxylic acid Ethers Ethers are relatively stable and often used as solvents Cr 3 periodinane PCC Jones eagent C 2 Cl 2 Ac I Ac 3 + or 2 alcohols form ketones 1 alcohols form aldehydes 2 alcohols form ketones 1 alcohols form carboxylic acids diethyl ether 3 C methyl t-butyl ether tetrahydrofuran (TF) 1,2-epoxycyclohexane added to gasoline to increase octane rating Na 2 Cr 2 7 2, C 3 C

4 2014 Gregory Cook Ether Nomenclature Ethers are named by naming the two alkyl groups and calling it an ether. Ethers as substituents are alkoxy groups. eactions of Alcohols - Ether ynthesis Na C 3 I C3 N 2 3 C methyl ethyl ether diethyl ether C 3 isopropyl phenyl ether 3 C p-dimethyoxybenzene 4-isopropoxycyclohex-1-ene eactions of Ethers - Epoxide opening Thiols and ulfides N 2 3 C 3 C C 3 X X methanethiol dimethyl sulfide cysteine m-cpba 3 + diallyldisulfide found in garlic C3 allyl methyl sulfide metabolite - garlic breath + C 3 I C3 21 methyl phenyl sulfide 22 Thiols and Disulfides in Biology air is protein with disulfide bonds + thiols [], I 2 [ed], Zn, + disulfide hair proteins crosslinks broken permanently curled N 4 curl hair and treat with hydrogen peroxide 23 24

5 air is protein with disulfide bonds hair proteins crosslinks broken permanently curled N 4 curl hair and treat with hydrogen peroxide 24