有機(jī)化學(xué)：第七章-1Halogen-Substituted Hydrocarbons

1、Chapter Seven Halogen-Substituted HydrocarbonsNomenclature of Halogen-Substituted HydrocarbonsStructure of Halogen-Substituted Hydrocarbons Preparation of Halogen-Substituted Hydrocarbons.Chemical Properties of Halogen-Substituted HydrocarbonsClassification of Halogen-Substituted HydrocarbonsClassif

2、ication of Halogen-Substituted HydrocarbonsHalogen-substituted hydrocarbon ：The compound that one (or more) hydrogen atom in a hydrocarbon is substituted by halogen atom.鹵代烴鹵代烴Classification:a. According to the hydrocarbon:XAlkyl halogen: CH3CH2CH2XRHCCHXRHCCHCH2XRCCCH2XAlkenyl halogen: Alkynyl halo

3、gen:Aryl halogen:XClassification of Halogen-Substituted Hydrocarbons2. According to the degree of carbonCH2XRCHXRRCRR2R3XPrimaryhalideTertiary halideSecondary halideReviewCH2XRCHXRRCRR2R3XPrimaryhalide 1 RX Tertiary halide 3 RX Secondaryhalide 2 RX H2CCHXXAryl halidesVinyl halidesH2CCHCH2XCH2XBenzyl

4、 halides Allyl halidesChapter Seven Halogen-Substituted HydrocarbonsNomenclature of Halogen-Substituted HydrocarbonsStructure of Halogen-Substituted Hydrocarbons Preparation of Halogen-Substituted Hydrocarbons.Chemical Properties of Halogen-Substituted HydrocarbonsClassification of Halogen-Substitut

5、ed HydrocarbonsNomenclature of Halogen-Substituted Hydrocarbons Alkyl halides are named in the same way as alkanes, by treating the halogen as a substituent on a parent chain. There are three rules:Rule 1: Find the longest carbon chain and name it as the parent. If a double or triple bond is present

6、, the parent chain must contain it.Rule 2 : Number the carbon atoms of the parent chain, beginning at the end nearer the first substituent, regardless of whether it is alkyl or halo. Assign each substituent a number to its position on the chain.Rule 3: If the parent chain can be properly numbered fr

7、om either end by rule 2, begin at the end nearer the substituent (either alkyl or halo) that has alphabetical precedence.For example:Nomenclature of Halogen-Substituted HydrocarbonsCH3CHCH2CHCHCH2CH3CH3CH3BrCH3CHCH2CHCHCH3CH3Cl5-Bromo-2,4-dimethylheptane2-Chloro-5-methylhexaneClBrBr1-Chlorocyclohexe

8、ne1,2-Dibromobenzene(R)-3-Chloro-2,3-dimethylpentaneChapter Seven Halogen-Substituted HydrocarbonsNomenclature of Halogen-Substituted HydrocarbonsStructure of Halogen-Substituted Hydrocarbons Preparation of Halogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted HydrocarbonsClassi

9、fication of Halogen-Substituted HydrocarbonsPreparation of Halogen-Substituted Hydrocarbons(a) Free Radical Substitution of Alkanes and Cycloslksnes :(b) Additions of Small Cycloalkanes:+ HBrBrFrom Alkanes and Cycloalkanes:CH3Br2+lightCH3BrCH3CHCH3CH3+Cl2lightCH3CCH3CH3Cl(a) Addition of Halogens to

10、Alkenes:Preparation of Halogen-Substituted Hydrocarbons(b) Hydrohalogenation of Alkenes:CH2CH+CH3Cl2CH2CHCH3ClClCCI4CH2CH+ HBrCH3CH3CHCH3BrCH2CH+HBrCH3CH3CH2CH2BrROOR(c) Free Radical Substitution of Alkenes:+NBSBrCCI4From Alkenes :(a) Hydrohalogenation of Alkynes:Preparation of Halogen-Substituted H

11、ydrocarbonsCH3CH2CHBr/HOAcCH3CH2CCH3BrBrCHCH3CH2CCH2BrHBr(a) Aromatic Halogenation:Br2+FeBr3BrHBr+(b) Halogenation of Alkylbenzene Side Chains:CH2CH3NBS+CCl4hvBrFrom Alkynes :From Aromatic Hydrocarbons :Preparation of Alkyl Halides from Alcohols: The most general method for preparing alkyl halides i

12、s to make them from alcohols (醇醇). The simplest method for converting an alcohol to an alkyl halide involves treating the alcohol with HCl, HBr, or HI.Preparation of Halogen-Substituted Hydrocarbonsthionyl chloride 亞硫酰氯亞硫酰氯ROH + HXRX + H2O Primary and secondary alcohols are best converted into alkly

13、 halides by treatment with such reagents as thionyl chloride (SOCl2) or phosphorus trihalides (PX3).ROH+ PX3RX + HOPX2ROH+ SOCl2RCl + SO2+ HClChapter Seven Halogen-Substituted HydrocarbonsNomenclature of Halogen-Substituted HydrocarbonsStructure of Halogen-Substituted Hydrocarbons Preparation of Hal

14、ogen-Substituted HydrocarbonsChemical Properties of Halogen-Substituted HydrocarbonsClassification of Halogen-Substituted Hydrocarbons Since halogens are more electro-negative than carbon. The C-X bond is therefore polar, with the carbon atom bearing a slight positive charge (+) and the halogen a sl

15、ight negative charge (-).Structure of Halogen-Substituted Hydrocarbons1. The structure of alkyl halides (鹵代烷鹵代烷)2. The structure of vinyl halides and aryl halidesStructure of Halogen-Substituted HydrocarbonsC CX0 00 000. . . .vinylic halidesaryl halidesCCHXX Vinylic and arylic C-X bonds are more sta

16、ble than the corresponding saturated bonds and are therefore more difficult to be brokenp-conjugated effectXChapter Seven Halogen-Substituted HydrocarbonsNomenclature of Halogen-Substituted HydrocarbonsStructure of Halogen-Substituted Hydrocarbons Preparation of Halogen-Substituted HydrocarbonsChemi

17、cal Properties of Halogen-Substituted HydrocarbonsClassification of Halogen-Substituted Hydrocarbons1. Nucleophilic Substitutions of Alkyl HalidesChemical Properties of Halogen-Substituted HydrocarbonsRX+NuSNRNu + x Alkyl halides can undergo substitution of the X group by the nucleophile (Nu:)Nucleo

18、philes = OH 、RO 、NO3 、NH3、H2ORI RBr RCl RFReactivity:Substrate 底物底物L(fēng)eaving group 離去基團(tuán)離去基團(tuán)Chemical Properties of Halogen-Substituted Hydrocarbons堿性水解制備醇，一般堿性水解制備醇，一般伯，仲伯，仲鹵代烴鹵代烴Williamson合成不對(duì)稱醚，合成不對(duì)稱醚，伯鹵代烴伯鹵代烴生成腈生成腈(nitrile)，碳鏈增長(zhǎng)的反應(yīng)碳鏈增長(zhǎng)的反應(yīng)生成硫醚生成硫醚 (sulfide)ROH + NaXROEt + NaXRCN + NaXRI + NaX合成碳鏈增長(zhǎng)的炔

19、烴合成碳鏈增長(zhǎng)的炔烴硝酸酯硝酸酯 (nitrate)RSCH3 + NaXCCRR+NaXRONO2 + AgXNegatively charged Nu:- RX +NaCNNaOHH2ONaOEtEtOHCH3COCH3NaIEtOHNaSCH3NaC CHEtOHAgNO3P219Chemical Properties of Halogen-Substituted Hydrocarbons This reaction can be used to differentiate(區(qū)別區(qū)別) halogen- substituted hydrocarbons.PhCH2H2CCHCH22RX1

20、RXCC3RXRPhenomenonRX + AgNO3RONO2 + AgXEtOHGive precipitate immediatelyGive precipitate after heatingGive precipitate after heating for a long timeNo reactionChemical Properties of Halogen-Substituted HydrocarbonsRelatively reactivity: 1o RX 2o RX 3o RX This reaction can be used to differentiate(區(qū)別區(qū)

21、別) chloro-substituted hydrocarbon and bromo-substituted hydrocarbon. The driving force of this reaction is the different solubility in acetone: NaI can dissolve in acetone, NaBr and NaCl are insolublein acetone. CH3CHCH3Br+NaI丙丙 酮酮CH3CHCH3I+NaBr (Cl)Acetone(Cl)RX +HORRNH3X-RORNH3- H+RNH2 + NH4X-RORN

22、H3HHXX+ HXChemical Properties of Halogen-Substituted HydrocarbonsNeutral Nu:2. The SN2 Reaction and SN1 ReactionChemical Properties of Halogen-Substituted Hydrocarbons(1) The SN2 Reaction-雙分子反應(yīng)雙分子反應(yīng) (bimolecular)CH3BrH2ONaOHCH3OH= kCH3BrOH- lets look at the kinetics of a simple nucleophilic substitu

23、tion of CH3Br with OH- to yield CH3OH plus Br -. the rate of disappearance of reactant (反應(yīng)物反應(yīng)物) is equal to a constant of k times the alkyl halide concentration (濃度濃度) times the hydroxide ion (OH-) concentration. So the rate of this reaction is dependent on the concentrations of two species, and the

24、 reaction is second-order(二級(jí)二級(jí)) reaction.The mechanism of SN2:Chemical Properties of Halogen-Substituted HydrocarbonsThe reaction takes place in a single step without intermediates.2-Bromobutane2-Butanol(1). This reaction occurs through a transition state in which the new HO-C bond is partially form

25、ing at the same time that the old C-Br is partially breaking.transition state(S)-(R)-(2). The stereochemistry at carbon is inverted. ( Walden Inversion)沃爾頓翻轉(zhuǎn)沃爾頓翻轉(zhuǎn)Chemical Properties of Halogen-Substituted Hydrocarbons The characteristics of the SN2 reaction:(a) The substrate (RX) : steric effect in

26、the SN2 reactionCLNuSN2 transition state:sterically hindered alkyl halideatom is “shielded” nucleophile is difficult to approach the energy of T.S. is high the reaction is slowCH3X 1 RX 2 RX 3 RXReactivity of alkyl substrates:Chemical Properties of Halogen-Substituted HydrocarbonsH2CCHCH2XPhCH2XHHHHLNuHighest reactivityXH2CCHXP, conjugated effect, reinforce the C-X bonds no reactionThe relative reactivity of substrates in SN2: PhCH2XCH2=CHCH2XCH3 1RX 2 RX 3RXChemical Properties of Halogen-Substituted Hydrocarbons(b) The nucleophile (親核試劑親核試劑) :High nucleophilicity (親核性親核性) is favorable to t