Naming with Multiple halides p 222 If more than one of the same kind CHaCHCHCHCH CH3 of halogen is 23456 present, use prefix CH. d i. tri, tetra 2.3-Dichloro-4-methylhexane · If there are e teers. arcus celn several different CH Br alogens. number CHOCHCHOCHOCHCH them and list them 654321 in alphabetical 2-Bromo-5-methylhexane order (NOT 5-bromo-2-methylhexane) e Thaman -3tDois Coe
• If more than one of the same kind of halogen is present, use prefix di, tri, tetra • If there are several different halogens, number them and list them in alphabetical order Naming with Multiple Halides p.222
7. 2 Preparation of Alkyl Halides: p 58 Radical chlorination of alkanes Alkane Cl2 or br2, heat or light replaces: Via free radical mechanism It is usually not a good idea to plan a synthesis that uses this method - hard to contro hv CH Cl CH3CI HCI CHoCI2 HCI 2 CHCla HCl Clo CCL Hcl Thomson· Brooks cole
• Alkane + Cl2 or Br2, heat or light replaces:Via free radical mechanism • It is usually not a good idea to plan a synthesis that uses this method -Hard to control 7.2 Preparation of Alkyl Halides: Radical Chlorination of Alkanes p.58
Reactions favor replacing the hydrogen at the most highly substituted carbons(not absolute) + 16% hv /c HCl 28 22%0
Reactions favor replacing the hydrogen at the most highly substituted carbons (not absolute): 28% 34% 16% 22% hn / Cl2 －HCl Cl Cl Cl Cl + + +
Relative reactivity Order parallels stability of radicals Reaction distinction is more selective with bromine than chlorine H H H R R一C-HR-C—HR-C-HR-C R-C R H R H R Primary Secondary Tertiary Primary Secondary Tertiary 3.5 5.0 Reactivity Stability
Relative Reactivity • Order parallels stability of radicals • Reaction distinction is more selective with bromine than chlorine
Chain reaction p. 58 R一H+X2-一RX+HX Homolitic fussion: initiate step Ⅹ 2X. Chain propagating step RH+Ⅹ.—-R.+HX R+X RⅩ+X Chain terminating step R.+Ⅹ RX R·+R R-R Ⅹ·+Ⅹ.一
R H + X2 RX + HX X2 2X. R H HX RX + X. R. + R. + X2 + X. R R R. + X. RX R. + R. X. + X. X2 Homolitic fussion: initiate step hv Chain reaction Chain propagating step: Chain terminating step: p.58