红外光谱法讲稿1(1293).ppt

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1、红外光谱1一、红外解析步骤1、不饱和度（U）的确定不饱和度：有机分子中碳原子的饱和程度。即分子结构式中距达到饱和所缺少的一价元素的“对”数。角标数字代表元素价数。例如：C4H5N、C9H15NH:1价；O:2价；N:3价；C:4价2以3000cm1为界:高于3000cm1为不饱和碳C-H伸缩振动吸收可能为烯,炔,芳香化合物低于3000cm1一般为饱和C-H伸缩振动吸收（1）首先依据谱图推出化合物碳架类型（2）分析3300~2800cm1区域C-H伸缩振动吸收2、未知物结构确定3(3)若在稍高于3000cm1有吸收,则应在2250~1450cm1频区分析不饱和碳碳键的伸缩

2、振动吸收特征峰炔2200~2100cm1烯1680~1640cm1芳环1600,1580,1500,1450cm1烯或芳香化合物则应解析指纹区1000~650cm1频区以确定取代基个数和位置4(5)解析时应注意把描述各官能团的相关峰联系起来，以准确判定官能团的存在如2820，2720和1750~1700cm1的三个峰说明醛基的存在(4)碳骨架类型确定后,再依据其他官能团,如C=O,O-H,C-N等特征吸收来判定化合物的官能团5Whenyouanalyzethespectra,itiseasierifyoufollowaseriesofstepsinexaminingeac

3、hspectrum.1.LookfirstforthecarbonylC::Oband.Lookforastrongbandat1820-1660cm-1.Thisbandisusuallythemostintenseabsorptionbandinaspectrum.Itwillhaveamediumwidth.Ifyouseethecarbonylband,lookforotherbandsassociatedwithfunctionalgroupsthatcontainthecarbonylbygoingtostep2.IfnoC::Obandispresent,checkf

4、oralcoholsandgotostep3.2.IfaC::Oispresentyouwanttodetermineifitispartofanacid,anester,oranaldehydeorketone.Atthistimeyoumaynotbeabletodistinguishaldehydefromketoneandyouwillnotbeaskedtodoso.ACIDLookforindicationsthatanO-Hisalsopresent.Ithasabroadabsorptionnear3300-2500cm-1.Thisactuallywillover

5、laptheC-Hstretch.TherewillalsobeaC-Osinglebondbandnear1100-1300cm-1.Lookforthecarbonylbandnear1725-1700cm-1.6ESTERLookforC-Oabsorptionofmediumintensitynear1300-1000cm-1.TherewillbenoO-Hband.ALDEHYDELookforaldehydetypeC-Habsorptionbands.ThesearetwoweakabsorptionstotherightoftheC-Hstretchnear285

6、0cm-1and2750cm-1andarecausedbytheC-HbondthatispartoftheCHOaldehydefunctionalgroup.Lookforthecarbonylbandaround1740-1720cm-1.KETONETheweakaldehydeCHabsorptionbandswillbeabsent.LookforthecarbonylCObandaround1725-1705cm-1.3.Ifnocarbonylbandappearsinthespectrum,lookforanalcoholO-Hband.ALCOHOLLookf

7、orthebroadOHbandnear3600-3300cm-1andaC-Oabsorptionbandnear1300-1000cm-1.4.IfnocarbonylbandsandnoO-Hbandsareinthespectrum,checkfordoublebonds,C::C,fromanaromaticoranalkene.7ALKENELookforweakabsorptionnear1650cm-1foradoublebond.Therewillb