Week02-Lecture01 UV-Vis spectrometry

1、light in a solution of . The beam intensity becomes weaker as it passes through solutionIIIITbcA00loglog -logAbsorbance is additive:Atotal = A1 + A2 . = 1bc1 + 2bc2 .In a 2 component mixture:A1 = 1, 1bc1 + 2, 1 bc2A2 = 1, 2 bc1 + 2, 2 bc2(1) - analyte associates, dissociates or reacts to give molecu

2、le with different 化学因素有：1. 溶液浓度过高引起的偏离；2. 化学反应（如水解、解离）引起的偏离；(2) - stray light, polychromatic radiation or noise物理因素有：物理因素有：1. 非单色光引起的偏离；非单色光引起的偏离；2. 非平行入射光引起的偏离；非平行入射光引起的偏离；3. 介质不均匀引起的偏离；介质不均匀引起的偏离；引起分子电子能级引起分子电子能级跃迁的光谱称为电跃迁的光谱称为电子吸收光谱，其波子吸收光谱，其波长位于紫外长位于紫外-可见光可见光区，即紫外区，即紫外-可见光可见光谱。谱。Wavelength range

3、 of electronic spectra: 10800 nm.(10200 nm)(200400 nm)(400800 nm)Types of electronic transitions of organic molecules OOClClClClCH3CH3CH3CH3CH3CH3+OOClClClClCH3CH3CH3CH3CH3CH3(Yellow)(Colorless)(Dark red)a. Strength (紫外吸收带的强度紫外吸收带的强度) 紫外光谱中吸收带的强度标志着相应电子能级紫外光谱中吸收带的强度标志着相应电子能级跃迁的几率，遵从跃迁的几率，遵从Lamber-Be

4、er定律：定律：A= lg(I0/I) = lg(1/T) = abc b. 紫外光谱的表示法紫外光谱的表示法 紫外光谱以图或者数据表示。紫外光谱以图或者数据表示。c. UV terminology (常用术语常用术语) chromophore ()20 Auxchrome ()是指本身不产生紫外吸是指本身不产生紫外吸收的基团，但是与生色团相连时，使生色团的收的基团，但是与生色团相连时，使生色团的吸收向长波方向移动，且吸收强度增大。吸收向长波方向移动，且吸收强度增大。常见助色团有：常见助色团有：-OH、-OR、-NHR、-SH、SR、-Cl、-Br、-I等。等。Red shift ()：由于有

5、机物的结构发生变化：由于有机物的结构发生变化（如取代基的变更）或受到溶剂的影响时，其吸收（如取代基的变更）或受到溶剂的影响时，其吸收带最大吸收波长向长波方向移动的效应。带最大吸收波长向长波方向移动的效应。 ()：吸收带最大吸收波长向短波：吸收带最大吸收波长向短波方向移动，与红移相反的效应。方向移动，与红移相反的效应。Hyperchromic effect () ：使吸收带得：使吸收带得吸收强度增大的效应。反之为吸收强度增大的效应。反之为()。：在紫外光谱中凡摩尔吸光：在紫外光谱中凡摩尔吸光系数大于系数大于104的吸收带称为强带，其电子跃迁为允许的吸收带称为强带，其电子跃迁为允许跃迁。反之，低于

6、跃迁。反之，低于1000的称为的称为weak band (，其电子跃迁往往为禁阻跃迁其电子跃迁往往为禁阻跃迁。a. The formation of the conjugated system b. Hyperconjugation 当烷基与当烷基与共轭体系相连时，可以使波长产生共轭体系相连时，可以使波长产生少量红移。这是因为烷基的少量红移。这是因为烷基的 电子与共轭的电子与共轭的 电子电子云发生一定程度的重叠，扩大的共轭范围，使得云发生一定程度的重叠，扩大的共轭范围，使得 *的能量降低，吸收红移。的能量降低，吸收红移。c. Solvent Effect下表为溶剂对丙酮紫外吸收光谱的影响。下表

7、为溶剂对丙酮紫外吸收光谱的影响。 正己烷正己烷 CHCl3 CH3OH H2O * max/nm 230 238 237 243 n * max/nm 329 315 309 305选择溶剂时注意下列几点：u 溶剂应能很好地溶解被测试样，溶剂对溶质应该是惰性的。即所成溶液应具有良好的化学和光化学稳定性；u 在溶解度允许的范围内，尽量选择极性较小的溶剂；u 溶剂在样品的吸收光谱区应无明显吸收。d. Spatial EffectsNO2NO2CH3NO2C2H5NO2C4H9C4H9max890060705300640e. The impact of pH on the ultraviolet s

8、pectrum OOOHHO酸性介质 无色碱性介质 粉红色O-OOH-OOH-Tungsten halogen lampDeuterium lampSelenium cellPhotomultipliera. Single-beam spectrophotometerb. Double-beam spectrophotometerc. Dual-wavelength spectrophotometerd. Multichannel SpectrophotometerNo scanning - simple and fastMore expensiveLimited resolutiona. U

9、sing standard K2CrO4 solution to the absorbance scale; b.Using didymium glass or holmium oxide glass filter to the wavelength scale.1. Saturated hydrocarbons and their substituted derivatives2. Simple unsaturated compounds在在不饱和烃类分子中，当有两个以上的双键不饱和烃类分子中，当有两个以上的双键共轭时，随着共轭系统的延长，共轭时，随着共轭系统的延长， *跃迁的吸跃迁的吸收带

10、收带 将明显向长波方向移动，吸收强度也随之增将明显向长波方向移动，吸收强度也随之增强。在强。在共轭体系中，共轭体系中， *跃迁产生的吸收带又跃迁产生的吸收带又称为称为K带。带。 简单的简单的的分子轨道的分子轨道C-O之间除之间除 键键电子外，还有一对电子外，还有一对 电子。电子。 可产生可产生*、 n* 、n*三个吸收带，三个吸收带， n*吸收带又称吸收带又称R带，落于近紫外或紫外光区带，落于近紫外或紫外光区。3. Conjugated dienes Base value for heteroannulardiene214Base value for homoannular diene253I

11、ncrementsDouble bondextending conjugation+ 30Alkylsubstituentor ring residue+ 5Exocyclicdouble bond+ 5acetategroup+ 0Ethergroup+ 6Thioethergroup+ 30bromine,chlorine+ 5tertiary aminegroup+ 30波长增加因素波长增加因素 max/nm 1. 开链或非骈环共轭双烯基本值 217双环上烷基取代增加值 +5环外双烯 +52. 同环共轭双烯或共轭多烯骈环异环共轭双烯基本值 214同环共轭双烯基本值 253延长一个双键增加

12、值 +30烷基或环残基取代 +5环外双键 +5助色基团-OAc 0-OR +6-SR +30-Cl、-Br +5-NR2 +60共轭双烯基本值共轭双烯基本值 217 4个残基取代个残基取代 +54 计算值计算值 237(238)AcO同环共轭双烯基本值同环共轭双烯基本值 253 5个烷基取代个烷基取代 +54 3个环外双键个环外双键 +53 延长一个双键延长一个双键 +30 计算值计算值 353(355)4. , -unsaturated aldehydes and ketones环外双键增加值 +5双键同环共轭增加值 +39延长一个共轭双键增加值 +30取代基位-位-位-位烷基或环烷基+10

13、+12+18-OH+35+30+30+50-OAc+6+6+6-OR+30+35+17+31-SR+85-Cl+15+12-Br+25+30-NR2+95计算举例：计算举例：六元环六元环,-不饱和酮基本值不饱和酮基本值 215 2个个取代取代 +122 1个环外双键个环外双键 +5 计算值计算值 244(251)OO直链直链,-不饱和酮基本值不饱和酮基本值基基本值本值 215 1个延长共轭双键个延长共轭双键 +30 1个烷基个烷基取代取代 +18 1个烷基个烷基取代取代 +18 计算值计算值 281(281)环外双键增加值 +5双键在五元环或七元环内增加值 +5延长1共轭双键增加值 +30-或

14、-位烷基取代增加值 +18-位OCH3、OH，Br，Cl取代增加值 +1520-位OCH3，OR取代增加值 +30-位N(CH3)2取代增加值 +605. , -unsaturated carboxylic acids, esters, amides例如：例如：CH3-CH=CH-CH=CH-COOH单取代羧酸基准值单取代羧酸基准值 208延长一个共轭双键延长一个共轭双键 +30烷基取代烷基取代 +18计算值计算值 256 (254)OOHa,b-unsaturatedketoneBase value: 202 nmOOHa,b-unsaturated ketoneBase value: 20

15、2 nma-hydroxy group: 35 nmOOHa,b-unsaturated ketoneBase value: 202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsaturated ketoneBase value:202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsaturated ketone249 nmOBase value:202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsatur

16、ated ketone249 nmBase value:215 nmOBase value:202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsaturated ketone249 nmBase value:215 nma-alkyl group: 10 nmOBase value:202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsaturated ketone249 nmBase value:215 nma-alkyl group: 10 nmb-alkyl gr

17、oup: 12 nmOBase value:202 nma-hydroxy group: 35 nmb-alkyl group: 12 nmOOHa,b-unsaturated ketone249 nmBase value:215 nma-alkyl group: 10 nmb-alkyl group: 12 nm237 nmMeOMea,b-unsaturated ketoneMeOMeBase value:215 nma,b-unsaturated ketoneMeOMeBase value:215 nma-alkyl group: 10 nma,b-unsaturated ketoneM

18、eOMeBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nma,b-unsaturated ketoneMeOMeBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic double bonds: 10 nmMeOMeMeOMea,b-unsaturated ketoneMeOMeBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic

19、 double bonds: 10 nm 259 nma,b-unsaturated ketoneMeOMeBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic double bonds: 10 nm 259 nmOHOa,b-unsaturated ketoneMeOMeOHOBase value:215 nma,b-unsaturated ketoneBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyc

20、lic double bonds: 10 nm 259 nmMeOMeOHOBase value:215 nmb-hydroxy group: 30 nma,b-unsaturated ketoneBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic double bonds: 10 nm 259 nmMeOMeOHOBase value:215 nmb-hydroxy group: 30 nmb-alkyl group: 12 nma,b-unsaturated ketoneBase value

21、:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic double bonds: 10 nm 259 nmMeOMeOHOBase value:215 nmb-hydroxy group: 30 nmb-alkyl group: 12 nm 257 nma,b-unsaturated ketoneBase value:215 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmTwo exocyclic double bonds: 10 nm 259 nmOOBase val

22、ue:215 nma,b-unsaturated ketoneOBase value:215 nmDouble bondExtending conjug.: 30 nma,b-unsaturated ketoneOBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nma,b-unsaturated ketoneOBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nma,b-un

23、saturated ketoneOBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-alkyl group: 18 nma,b-unsaturated ketoneOBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-alkyl group: 18 nmTwo exocyclic double bonds: 10 nmOOa

24、,b-unsaturated ketoneO 303 nma,b-unsaturated ketoneBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-alkyl group: 18 nmTwo exocyclic double bonds: 10 nmOOa,b-unsaturated ketone 303 nmBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg

25、-alkyl group: 18 nmg-alkyl group: 18 nmTwo exocyclic double bonds: 10 nmOOBase value:215 nma,b-unsaturated ketone 303 nmBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-alkyl group: 18 nmTwo exocyclic double bonds: 10 nmOBase value:215 nmDouble bondExtend

26、ing conjug. 30 nmb-alkyl group: 12 nmg-alkyl group:18 nmg-alkyl group:18 nmTwo exocyclic double bonds10 nmOBase value:215 nma-alkyl group: 10 nma,b-unsaturated ketone303 nmOOBase value:215 nma-alkyl group: 10 nm2 b-alkyl groups: 24 nma,b-unsaturated ketone 303 nmBase value:215 nmDouble bondExtending

27、 conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-alkyl group: 18 nmTwo exocyclic double bonds: 10 nmOOBase value:215 nma-alkyl group: 10 nm2 b-alkyl groups: 24 nm249 nma,b-unsaturated ketone 303 nmBase value:215 nmDouble bondExtending conjug.: 30 nmb-alkyl group: 12 nmg-alkyl group: 18 nmg-a

28、lkyl group: 18 nmTwo exocyclic double bonds: 10 nmOa,b-unsaturated ketoneOBase value:202 nma,b-unsaturated ketoneOBase value:202 nma-alkyl group: 10 nm a,b-unsaturated ketoneOBase value:202 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nma,b-unsaturated ketoneOBase value:202 nma-alkyl group: 10 nmTwo

29、 b-alkyl groups: 24 nmExocyclic double bond: 5 nmOa,b-unsaturated ketoneO 241 nma,b-unsaturated ketoneBase value:202 nma-alkyl group: 10 nmTwo b-alkyl groups: 24 nmExocyclic double bond: 5 nmOOOCHOBrOOAcOOOCHOBrOOAcOOOCHOBrOOAca,b-unsaturated ketoneOOOCHOBrOOAcOOOCHOBrOOAcBase value:215 nma,b-unsatu

30、rated ketoneOOOCHOBrOOAcOOOCHOBrOOAcBase value:215 nma-alkoxy (OMe): 35 nma,b-unsaturated ketoneOOOCHOBrOOAcOOOCHOBrOOAcBase value:215 nma-alkoxy (OMe): 35 nmb-alkoxy (OMe): 30 nma,b-unsaturated ketoneOOOCHOBrOOAcOOOCHOBrOOAcBase value:215 nma-alkoxy (OMe): 35 nmb-alkoxy (OMe): 30 nmDouble bond exte

31、nding conj.: 30 nma,b-unsaturated ketoneOOOCHOBrOOAcOOOCHOBrOOAcBase value:215 nma-alkoxy (OMe): 35 nmb-alkoxy (OMe): 30 nmDouble bond extending conj.: 30 nmg alkyl group: 18 nma,b-unsaturated ketoneOOOCHOBrOOAcBase value:215 nma-alkoxy (OMe): 35 nmb-alkoxy (OMe): 30 nmDouble bond extending conj.: 3

32、0 nmg alkyl group: 18 nmHomodiene: 39 nm a,b-unsaturated ketoneOOOCHOBrOOAc367 nma,b-unsaturated ketoneBase value:215 nma-alkoxy (OMe): 35 nmb-alkoxy (OMe): 30 nmDouble bond extending conj.: 30 nmg alkyl group: 18 nmHomodiene: 39 nmONHMeBrCOOCH3 trieneONHMeBrCOOCH3Base value (heteroannular diene):21

33、4 nm trieneONHMeBrCOOCH3Base value (heteroannular diene):214 nmDouble bond extending conjugation: 30 nm trieneONHMeBrCOOCH3Base value (heteroannular diene):214 nmDouble bond extending conjugation: 30 nmOalk group: 6 nm trieneONHMeBrCOOCH3Base value (heteroannular diene):214 nmDouble bond extending c

34、onjugation: 30 nmOalk group: 6 nmN(Alk)2: 60 nm trieneONHMeBrCOOCH3 trieneBase value (heteroannular diene):214 nmDouble bond extending conjugation: 30 nmOalk group: 6 nmN(Alk)2: 60 nm5 alkyl residues: 25 nmONHMeBrCOOCH3ONHMeBrCOOCH3ONHMeBrCOOCH3ONHMeBrCOOCH3ONHMeBrCOOCH3 trieneBase value (heteroannu

35、lar diene):214 nmDouble bond extending conjugation: 30 nmOalk group: 6 nmN(Alk)2: 60 nm5 alkyl residues: 25 nm4 exocyclic double bonds: 20 nmONHMeBrCOOCH3355 nm trieneBase value (heteroannular diene):214 nmDouble bond extending conjugation: 30 nmOalk group: 6 nmN(Alk)2: 60 nm5 alkyl residues: 25 nm4 exocyclic double bonds: 20 nmNOOAcOO a,b-unsaturated ketoneNOOAcOOBase value: 202 nmNOOAcOOBase value: 202 nm