5 Chap 10 : Alcohols 10.1 Structure and nomenclature of alcohols 10.2 Physical properties of alcohols 10.3 Acidity and basicity of alcohols 10.4 Reactions of alcohols with active metals 10.5 Conversion of alcohols to haloalkanes and sulfonates 10.6 Acid-catalyzed dehydration of alcohols 10.7 The Pinacol rearrangement 10.8 xidation of alcohols 10.9 Thiols Alcohol(R) : -(hydroxyl) 기를포함하는화합물자연계에널리분포하는작용기 (glucose) 용도 - 연료첨가제, 알코올음료, 공업용매다른유기화합물의제조 (RX, RC=C 2, RC, RCR', RC, RCR') Thiol(RS) : -S(sulfhydryl or thiol) 기를포함하는화합물 C 2 5 S -스컹크의냄새 10.1 Structure and omenclature of Alcohol A. Structure sp 3 혼성화된탄소에결합된 - (hydroxyl, 하이드록시 ) 기를가짐 C sp 3 sp 3 δ - δ + C = ~ 109.5 o 는 2 쌍의 nonbonding electron 을가지므로 basic 혹은 nucleophilic 한성질을띄며, 보다전기음성도가크므로 δ - 가발달된다. 는 acidic 한성질을띄며, 보다전기음성도가작으므로 δ + 가발달된다.
6 B. omenclature IUPAC 명 : -기를포함하는가장긴탄소사슬을모체 alkane으로선정하고, -에가까운쪽부터번호를매김모체 alkane의 -e -ol로교체관용명 : Alkyl + alcohol 1-Propanol 2-Propanol 2-Methyl-1-propanol 2-Methyl-2-propanol (Propyl alcohol) (Isopropyl alcohol) (Isobutyl alcohol) (tert-butyl alcohol) 1-Methylcyclopentanol (1R,2R)-2-Methylcyclohexanol Alcohol의분류 : -가결합된탄소에치환된 alkyl (or aryl) 기의개수에따라 primary(1차, 1 o ), secondary(2차, 2 o ), tertiary(3차, 3 o ) 로분류 C 2 Isobutyl alcohol (1 o ) Secondarybutyl alcohol (2 o ) Cyclopropylmethanol (1 o ) 1-Methylcyclopentanol (3 o ) Diol, triol, unsaturated alcohol 의명명법 : Diol, triol 의명명 - 모체 alkane 명 + diol (or triol) 1,2-Ethanediol 1,2-Propanediol 1,2,3-Propanetriol (Ethylene glycol) (Propylene glycol) (Glycerol) Unsaturated alcohol의명명 : 모체 alkane의 -an -en, -e -ol -기는 C=C보다우선권을가지므로 -기가가장낮은숫자로명명됨 C 2 CC 2 2-Propen-1-ol (E)-2-exen-1-ol 3-Buten-2-ol
7 10.2 Physical Properties of Alcohols Alcohol(R) : -의편극으로인하여극성을가짐. 분자간수소결합으로인하여비슷한분자량의다른화합물보다끓는점이증가하고, 물에대한용해도가높음. intermolecular hydrogen bonding 3 C C 3 수소결합의세기 = ~ 5 kcal/mol cf. - 공유결합의세기 = 118 kcal/mol C 3 Table 10.1 : Boiling point and solubility in 2 of alcohol and hydrocarbon i) 분자량이비슷할때 alcohol은 alkane보다끓는점이훨씬높다. C 3 C 2 C 3 C 3 C 3 C 3 C 2 bp -42 o C bp -24 o C bp 78 o C ii) 분자량이증가할수록분자들사이의분산력이증가하므로 alcohol의끓는점은증가한다. C 3 C 2 C 3 C 2 C 2 C 3 C 2 C 2 C 2 C 2 bp 78 o C bp 97 o C bp 138 o C iii) Alcohol은물과수소결합에의해상호작용하므로비슷한분자량의다른화합물보다물에대한용해도가훨씬크다. Alcohol의분자량이증가할수록분자내탄화수소의비율이증가하므로물에대한용해도는감소한다. C 3, C 3 C 2, C 3 C 2 C 2 C 3 C 2 C 2 C 2 C 3 C 2 C 2 C 2 C 2 Infinite soluble 8 g / 100 g 2 2.3 g / 100 g 2 예제 10.4 : Boiling point of 1 o, 2 o, 3 o alcohol 문제 10.5 : rder of solubility in 2
8 10.3 Acidity and Basicity of Alcohols R : 약산 ( + donor) 과약염기 ( + acceptor) 의두가지기능을가짐 1) Acidity of alcohol C 3 + 2 C 3 + 3 + K a = [C 3 ] [ 3 + ] [C 3 ] = 10-15.5 pk a = -logk a = 15.5 Alcohol의산성도는분자량이커짐에따라감소하며, 산성이약하므로 sodium bicarbonate(ac 3 ) 나 sodium carbonate(a 2 C 3 ) 와같은염기와는반응하지않 는다. Table 10.2 : pk a value of some alcohols in dilute aqueous solution - C 3 C C 3 2 C 3 C 2 (C 3 ) 2 C (C 3 ) 3 C -7 4.8 15.5 15.7 15.9 17 18 2) Basicity of alcohol C 3 C 2 + 2 S 4 C 3 C 2 + S 4 Ethyloxonium ion pk a = -2.4 10.4 Reaction of Alcohols with Active Metals Alcohol 은활성금속혹은 sodium hydride(a) 와반응하여수소를발생시키고, 금속 alkoxide 를생성한다. C 3 + a C 3 a + + 1/2 2 sodium methoxide C 3 C 2 + a C 3 C 2 a + + 2 sodium ethoxide
9 Sodium alkoxide 의용도 - + 를뽑아내는염기로사용 친핵성시약으로도이용됨 Basicity : C 3 C 2 - a + < (C 3 ) 3 C - a + C 3 C + C 3 C 2 a + C 3 C a + + C 3 C 2 10.5 Conversion of Alcohols to aloalkanes and Sulfonates Alcohol(R-) haloalkane (R-X) : Aqueous 조건 - 할로젠산 (X =,, I) onaqueous 조건 - P 3 (phosphorus tribromde), S 2 (thionyl chloride) A. Reaction with,, and I Tertiary alcohol은수용성조건의상온에서,, I와빠르게치환반응하여 tertiary haloalkane을생성하는반면, primary와 secondary alcohol은가열조건에서치환반응이일어난다. 1) Reaction of tertiary alcohol and + 2 fast oxonium ion slow 3 o carbocation + 2 fast + Et 2 0 o C 1-Methylcyclohexanol 1-Chloro-1-methylcyclohexane 2) Reaction of primary, secondary alcohol and 2 + reflux slow Rearrangement ( 자리옮김 ) 을동반한 alcohol 의 bromoalkane 으로의전환 + heat 3-Pentanol 3-omopentane 2-omopentane (major product) (product of rearrangement) +
10 + + 2 2,2-Dimethyl-1-propanol (eopentyl alcohol) 2-omo-2-methylbutane B. Reaction with Phosphorus Tribromide Isobutyl alcohol + P 3 C 2 2 0 o C + 3 P 3 Isobutyl bromide Phosphoric acid Mechanism : + P P + P + 3 P 3 P + P 3 를이용한반응의특성 - 시약보다온화한조건에서일어남자리옮김 (rearrangement) 을대부분배제할수있음 1당량의 P 3 가 3당량의 alcohol과반응함 C. Reaction with Thionyl Chloride Conversion of alcohol to chloroalkane with S 2 - onaqueous 조건 (S)-2-ctanol + S Chlorosulfite S + (R)-2-Chlorooctane + 1st step : 의친핵체가 S 를공격하여 을이탈시킴. Retention( 보존 ) 2nd step : - 음이온이 chlorosulfite 를공격하여 S 2 기체를이탈시킴. Inversion( 반전 )
11 D. Formation of Aryl and Alkyl Sulfonates R S R S R S Sulfonyl chloride Sulfonic acid Sulfonate anion (strong acid) (weak base, stable anion, good leaving group) 1) Preparation of sulfonate from alcohol C 3 C 2 + S p-toluenesulfonyl chloride (tosyl chloride, Ts) C 3 C 2 2 C 3 C 2 S Ethyl p-toluenesulsonate (ethyl tosylate, EtTs) C 3 + + S C 3 Methanesulfonyl chloride (mesyl chloride, Ms) pyridine C 2 2 S C 3 + Py + - Cyclohexyl methanesulfonate (cyclohexyl mesylate, cyclohexylms) Sulfonate 의유용성 - poor leaving 인 기를대신하여친핵성치환반응에서 good leaving group 역할을수행함 2) ucleophilic substitution of sulfonate C 3 C 2 S C 3 + a + I acetone C 3 C 2 I + a + S C 3 Preparation of (R)-2-octyl acetate from (S)-2-octanol + Ts Ts pyridine C 3 C - a + (S)-2-ctanol (R)-2-ctyl acetate 문제 10.7 : S
12 10.6 Acid-Catalyzed Dehydration of Alcohols Alcohol(R) 의 기는산성조건 (85% 3 P 4, conc 2 S 4 ) 에서인접한 와 2 가이탈되는 dehydration( 탈수 ) 가일어난다. Reactivity of dehydration of alcohol : 1 o R < 2 o R < 3 o R C 3 C 2 2 S 4 180 o C C 2 C 2 + 2 2 S 4 140 o C + 2 C 3 C 3 C 3 C 2 S 4 50 o C C 3 C C 2 + 2 C 3 Dehydration of unsymmetrical alcohol + 85% 3 P 4 fast slow 2 + + 3 + 1st step : 산-염기반응에의하여 oxonium 중간체의생성 2nd step : good leaving인 2 의이탈에의하여 carbocation 중간체의생성 3rd step : 2 가염기로작용하여 deprotonation이일어나 alkene의생성전체반응은가역적으로일어나며, 이탈된 2 를 alkene과함께제거하여평형을오른쪽으로유도할수있다. Rearrangement 를동반한 1 o, 2 o alcohol 의 dehydration 2 S 4 140~170 o C 3,3-Dimethyl-2-butanol 2,3-Dimethyl-2-butene 2,3-Dimethyl-1-butene (80%) (20%) + Mechanism : 2 2 S 4-2 1,2-shift of C 3 2 2 Dehydration of 1-butanol with 2 S 4 : + 2 S 4 140 ~ 170 o C + + 56% 32% 12%
13 문제 10.9 : 2 S 4 가온 + 2 10.7 The Pinacol Rearrangement 1,2-Diol(glycol) 을 2 S 4 로처리할때 alkyl기의 rearrangement 및 2 의탈수가일어나 ketone 혹은 aldehyde가생성되는반응 2 S 4 + 2 2,3-Dimethyl-2,3-butanediol (Pinacol) 3,3-Dimethyl-2-butanone (Pinacolone) Mechanism : 2 S 1,2-shift 4-2 of C 3 - + 1st step : 2 S 4 에의한 기의 protonation으로 oxonium 중간체생성 2nd step : good leaving인 2 의이탈에의하여 3 o carbocation 중간체생성 3rd step : 의 nonbonding electron의도움을받아 C 3 의 1,2-shift가일어남 4th step : 로부터 deprotonation이일어나 pinacolone이생성됨 비대칭 1,2-diol 의 pinacol rearrangement 2 S 4-2 1,2-shift of - + 2-Methyl-1,2- propanediol 2-Methylpropanal 예제 10.10 : 2 S 4-2 spiro[4.5]decan-6-one