14 10.8 xidation of Alcohols 1 o Alcohol : RC 2 RC RC 2 o Alcohol : RR'C RCR' 3 o Alcohol : R 3 C o oxidation A. Chromic Acid 1) Formation of chromic acid Chromic acid는황산수용액에 chromium oxide( 3 ) 나 potassium dichromate (K 2 2 7 ) 을용해시켜제조된다. + 2 2 4 Chromium oxide Chromic acid K + K + + 2 4 2 2 2) xidation of alcohol by chromic acid Jones reagent = 황산수용액속의 chromic acid 대부분의유기화합물은물에잘녹지않으므로 chromic acid를이용한산화는 aq acetone에녹여반응시키며, 과량의 Jones시약을사용한다. 2 4 2, acetone 1-exanol exanal(not isolated) exanoic acid + + + 2 Menthol Alkyl chromate Menthone + C 3 1-Methylcyclohexanol C 3 o oxidation
15 xidation of aldehyde with chromic acid R C + 2 R C 2 4 R C R C + 3 + 2 B. Pyridinium Chlorochromate 1 o alcohol aldehyde : pyridinium chlorochromate(pcc) 3 + Cl + Cl 3 PCC : yellow solid, 보관이가능함 C 2 Cl 2 를반응용매로사용 1 차 alcohol 을 aldehyde 로까지만산화 Geraniol PCC/C 2 Cl 2 Geranial C. Periodic Acid xidation of Glycols Periodic acid( 과아이오딘산 ) : I 4, white crystalline solid(mp 122 o C) Glycol 을분해하여두개의 carbonyl 화합물을생성함 C C + I 4 C + C + I 3 + 2 periodic acid iodic acid xidation mechanism of cis-1,2-cyclohexanediol with periodic acid + I I + I 3 exanedial 1st step : Diol 과 periodic acid 의반응으로 5-membered periodate 생성 2nd step : 5- 원자고리 periodate 속에있는원자가전자들의재분배를통하여두
16 I 4 산화에의한 cis-, trans-isomer 의구분 + I 4 trans-decalindiol + I 4 cis-decalindiol 예제 10.12 : xidation of 1,2-diol with periodic acid + I 4 10.9 Thiols A. tructure Thiol(R-) : sp 3 혼성탄소에결합된 -(sulfhydryl) 기를가진화합물 ydrogen sulfide 3 C Methanethiol 93.3 o 100.3 o Thiol 화합물에서 = 93.3 o, C = 100.3 o 라는사실은 2 가산소속의 결합성궤도함수보다 2 가황속의결합성궤도함수가더상당히큰 p-character 를 가진다는것을나타낸다. B. omenclature Thiol의고전적명명 : mercaptan( 머캅탄 ) 수은을잡는 이라는의미 2C 6 5 + g (C 6 5 ) 2 g IUPAC명 : i) -기를포함하는가장긴탄소사슬을모체알케인으로선택하여 alkane+thiol로명명함 ii) - 기와 -기가동시에존재할경우 -기가우선권을가지며, -기는접두사 sulfanyl-로나나냄
17 관용명 : - 기를포함하는가장긴탄소사슬을모체알케인으로선택하여 alkyl+mercaptan 으로명명하며, - 기를접두사로사용할경우는 mercapto- 로표기함 1-Butanethiol 2-Methyl-1-propanethiol 2-ulfanylethanol (Butyl mercaptan) (Isobutyl mercaptan) (2-Mercaptoethanol) C. Physical Properties Thiol의물리적특성 : 1) - 결합의극성이낮으므로수소결합을하지않음 분자량이비슷할때 alcohol보다끓는점이낮음 Alcohol보다물이나다른극성용매에서용해도가낮음 Table 10.3 : Boiling point of thiol and alcohol Thiol bp, o C Alcohol bp, o C C 3 6 C 3 65 C 3 C 2 35 C 3 C 2 78 C 3 C 2 C 2 C 2 98 C 3 C 2 C 2 C 2 117 2) 악취를내는물질스컹크의냄새 : 2-butene-1-thiol, 3-methyl-1-butanethiol (isopentyl mercaptan) 분자량이작은 thiol은천연가스에냄새를풍기는물질로첨가하여사용됨 2-Propanethiol (Isopropyl mercaptan) 2-Methyl-2-propanethiol (tert-butyl mercaptan) D. Preparation and Thiol in Biological Molecule ucleophilic substitution of haloalkane with sodium hydrosulfide(a) C 3 (C 2 ) 8 C 2 I + a + ethanol C 3 (C 2 ) 8 C 2 + ai 2 or aq Et 2 + a
18 Thiol 화합물의용도 : odium thioglycolate - 머리카락의단백질의 disulfide 결합을끊는환원제 Calcium thioglycolate [(C 2 C - ) 2 Ca 2+ ] - 탈모제로사용 a + + I C 2 C a + C 2 C a + + ai odium hydrosulfide odium iodoacetate odium mercaptoacetate (odium thioglycolate) oxidation side chain of cysteine reduction (sodium thioglycolate) disulfide bond E. Acidity Thiol(R) : alcohol(r) 보다산성의세기가크다. i) Bond strength : σ - < σ - ii) 은 보다 orbital size가커서음이온전하의분산이잘일어나안정화된다. C 3 C 2 + 2 C 3 C 2 + 3 + pk a = 15.9 C 3 C 2 + 2 C 3 C 2 + 3 + pk a = 8.5 Preparation of sodium ethylsulfide C 3 C 2 + a + C 3 C 2 a + + 2 pk a = 8.5 pk a = 15.7
19 F. xidation Chemical bond of : xidation of thiol : R R Disulfide R R ulfinic acid R ulfonic acid 2 R + I 2 RR + 2 I 2 R + 1/2 2 RR + 2
20 Problems Physical properties of alcohols 10.19 rder of increasing boiling point C 3 C 2 C 3 C 3 C 3 C 3 C 2 C 3 C 10.21 olubility toward 2 10.26 Acidity 10.27 Basicity 10.31 Major product of reaction (b) + Cl 2 (c) + Cl (e) + 2 4 (g) 1) s 4, 2 2 2) I 4
21 10.35 ynthetic procedure (a) (e) C 2 C 2 Cl (i) C 2 Pinacol rearrangement 10.36 Mechanism of pinacol rearrangement BF 3. Et 2 + 2 ynthesis 10.37 (a) propene propanol by (1) hydroboration followed by oxidation with alkaline hydrogen peroxide (2) acid-catalyzed hydration 10.43 Reaction product a C 7 12 Ts