Chapter 6 lonic Reactions Nucleophilic substitution and elimination reactions of alkylhalides(卤代烃的亲核取代反 Because halogen 利消除 e more electronegative than carbon the carbon- halogen bond of alky halides is polarized; the carbon atom bears a partial positive charge, the halogen atom a partial negative charge 8X X=F. CI. Br
Chapter 6 Ionic Reactions--- Nucleophilic substitution and elimination reactions of alkylhalides (卤代烃的亲核取代反 Because halogen atoms are more electronegative 应和消除反应） than carbon, the carbon-halogen bond of alkyl halides is polarized; the carbon atom bears a partial positive charge, the halogen atom a partial negative charge. X X = F , Cl, Br, I + _
Table 6.1 Carbon-halogen bond lengths Bond Bond length(a) ChF 1.39 CH3CI 178 Ch2Br 193 CHaI 2.14
Table 6.1 Carbon-halogen bond lengths Bond Bond Length (A) CH3 F 1.39 CH3 Cl 1.78 CH3 Br 1.93 CH3 I 2.14
Vinyl halides(卤代乙烯)or phenyl halides(卤代苯基) X a vinylic halide A phenyl halide or ary halide ⅹ=F,C,Br,I Compounds in which a halogen atoms is bonded to an sp-hybridized carbon Carbon-halogen bond is difficult to break
Vinyl halides (卤代乙烯） or phenyl halides （卤代苯基） X X A vinylic halide A phenyl halide or ary halide X = F, Cl, Br, I Compounds in which a halogen atoms is bonded to an sp 2 -hybridized carbon Carbon-halogen bond is difficult to break
6.2 Physical properties of Very low s8rganessn balides They are miscible with each other and with other relatively nonpolar solvents CH,CI CHCI and cck are often used as solvents for nonpolar CHCI3 and CCl have a cumulative toxicity and are carcinogenIc Polyfluoroalkane癌铷质)的 boiling points, (Hexafluoroethane boils at -79o)
6.2 Physical properties of • Very low solubilities in water organic halides • They are miscible with each other and with other relatively nonpolar solvents • CH2Cl, CHCl3 and CCl4 are often used as solvents for nonpolar • CHCl3 and CCl4 have a cumulative toxicity and are carcinogenic. • Polyfluoroalkanes have low boiling points, • (Hexafluoroethane boils at –79o) (致癌物(质)的)
6.3 Reaction Mechanisms Mechanism of the reaction -The events that are postulated to take place at the molecular level as reactants become products If the reaction takes place in more than one step, then what are these steps, and what kinds of intermediates intervene between reactants and products?
6.3 Reaction Mechanisms Mechanism of the reaction—The events that are postulated to take place at the molecular level as reactants become products If the reaction takes place in more than one step, then what are these steps, and what kinds of intermediates intervene between reactants and products?