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1、P1：Hello everyone,welcome to organic spectroscopic analysis course.In last lecture,we have learned the selection rule of IR spectroscopy.In this lecture,we are going to learn the factors of influencing vibrational frequencies.大家好，歡迎學(xué)習(xí)今天的課程有機(jī)波譜分析。在上一堂課中，我們學(xué)習(xí)了紅外光譜的選率。這一節(jié)課，我們將學(xué)習(xí)影響振動頻率的因素。P2:The first f

2、actor is the status of molecule.Frequency in gas is bigger than that in liquid,and much bigger than that in solid.N-methylethylamine in its liquid state forms clusters,which makes C=O less stronger than that in solution，c=o shifts to lower frequency 1650cm-1 第一個因素是分子的狀態(tài)。氣態(tài)頻率大于液態(tài)并且遠(yuǎn)大于固體的頻率。N-甲基乙胺在液態(tài)時

3、形成聚合物，這使 C=O 的伸縮振動頻率不如溶液中強(qiáng)，c=o 移至低頻 1650cm-1 P3:For a simple harmonic oscillator,the frequency of a stretching vibration is given by an equation drived from Hooks law for a vibrating spring,where N is the Avogadros number,c is the velocity of light,K is the force constant,and a measure of the bond s

4、trength,is the reduced mass.對于簡諧振蕩，伸縮振動的頻率由霍克定律推導(dǎo)的彈簧方程式給出，其中 N 是阿伏加德羅數(shù)，c 是光速，K 是鍵力常數(shù)，量度鍵的強(qiáng)度，為折合的質(zhì)量。P4:Frequency decreases with increasing atomic weight.Frequency increases with increasing bond energy.頻率隨著原子量的增加而降低。頻率隨著鍵能的增加而增加。P5:Electron-withdrawing group makes the absorption peak shift to high fre

5、quency(Induction effect).吸電子基團(tuán)使吸收峰向高頻方向移動（誘導(dǎo)效應(yīng)）。P6:Due to the different electronegativity of the substituents,the distribution of electron clouds in the molecule is changed by the induction effect,which changes the force constant of the bond and the characteristic absorption frequency of the group.由

6、于取代基的電負(fù)性不同，分子中電子云的分布通過誘導(dǎo)效應(yīng)而改變，從而改變了鍵力常數(shù)和基團(tuán)的特征吸收頻率。The carbonyl group is a strongly polar group.Due to the large electronegativity of the oxygen atom,the electron cloud of the carbon-oxygen bond is approaching to oxygen atom.羰基是強(qiáng)極性基團(tuán)，由于氧原子的大負(fù)電性，碳-氧雙鍵的電子云接近氧。Generally,the force constant of the double

7、bond is greater than that of the single bond,so any effect of increasing the form of the single bond or enhancing the polarity will reduce the force constant of the carbonyl bond and cause the stretching vibration frequency of the carbonyl group to move to a low wave number.通常，雙鍵的鍵力常數(shù)大于單鍵的鍵力常數(shù)，因此，任何

8、增加單鍵性或增強(qiáng)極性的作用都會降低羰基的鍵力常數(shù)，并引起碳羰基伸縮振動頻率移至低波數(shù)。Conversely,when an electron-withdrawing group is connected to the carbon atom of the carbonyl group,the polarity of the carbonyl group is weakened,the carbon-oxygen bond force constant is increased,and the absorption band moves toward a high wavenumber.相反，當(dāng)

9、吸電子基團(tuán)連接到羰基的碳原子上時，羰基的極性減弱，碳-氧鍵力常數(shù)增加，吸收帶向高波數(shù)方向移動。P8:Conjugation effect:Conjugation effect often causes the polarity of the C=O double bond to increase,the double bond decreases,and the stretching vibration frequency moves to a low frequency direction(red shift).共軛效應(yīng)：共軛效應(yīng)常引起 C=O 雙鍵的極性增強(qiáng)，雙鍵性降低，伸縮振動頻率向低頻

10、方向移動（紅移）。The CC,C N bond existing in the conjugate system,its stretching vibration frequency also moves to the low wave number direction(red shift).存在于共軛體系中的 CC，C N 鍵，其伸縮振動頻率也向低波數(shù)方向移動（紅移）。P9:In these examples,p-conjugation makes C=O move to a low frequency.conjugation makes C=O move to a low frequen

11、cy too.在這些示例中，p-C=O 向低波數(shù)移動。C=O 向低波數(shù)移動。P12:Field effect is not through chemical bonds,but the effect of electrostatic fields through space.場效應(yīng)不是通過化學(xué)鍵，而是通過空間靜電場的作用。In the three-dimensional configuration of the molecule,only when the interesting groups in certain spatial structure are close to each oth

12、er,will the field effect occur.在分子的三維構(gòu)型中，只有當(dāng)某些空間結(jié)構(gòu)中所研究的基團(tuán)彼此靠近時，才會發(fā)生場效應(yīng) The field effect is not through chemical bonds,but the electrostatic fields of atoms or atomic groups interact through space.場效應(yīng)不是通過化學(xué)鍵，而是原子或原子團(tuán)的靜電場通過空間相互作用。P13:Steric effects includes ring force and steric hindrance Effects.立體效應(yīng)

13、包括環(huán)張力和空間位阻的影響 The double bond outside the ring moves to a higher wavenumber as the ring tension increases.隨著環(huán)張力的增加，環(huán)外的雙鍵向高波數(shù)移動。In contrast,the double bond inside the ring moves to a lower wavenumber as the ring tension increases 相反，當(dāng)環(huán)張力增加時，環(huán)內(nèi)部的雙鍵向低波數(shù)移動。P15:The effect of steric hindrance refers to th

14、e presence of certain groups in the molecule,when the steric hindrance affects the normal conjugation effect or hybrid state in the molecule,resulting in displacement of the vibrational band.位阻效應(yīng)是指當(dāng)分子中某些基團(tuán)的存在時，空間位阻影響分子中正常的共軛效應(yīng)或雜化狀態(tài)，導(dǎo)致振動帶發(fā)生位移。The introduction of the methyl group on the olefinic carbo

15、n prevents the carbonyl and the C=C double bond from being on the same plane.在烯烴碳上引入甲基導(dǎo)致羰基和 C=C 雙鍵不在同一平面上。Therefore,their degree of conjugation decreases,the double bond character of the carbonyl group increases.The vibration shifts to a high wave number.因此，它們的共軛度降低，羰基的雙鍵性增加，振動向高波數(shù)移動。P16:Transannula

16、r effects also influent the vibrational frequencies in IR spectra.跨環(huán)效應(yīng)也會影響紅外光譜中的振動頻率。P17:Due to the formation of hydrogen bonds,the force constant of the chemical bonds participating in the formation of hydrogen bonds is reduced,and the absorption frequency moves to a low wave number.由于氫鍵的形成，參與氫鍵形成的化學(xué)鍵的力常數(shù)降低，吸收頻率向低波數(shù)移動。At the same time,the change in dipole moment during vibration increases,so the absorption intensity increases.When hydrogen bonds are formed in the molecule,the absorption frequen