《有机化学》课程PPT教学课件（Organic Chemistry, William A. Price, Ph.D. PPT, La Salle University, L.G.WADE, JR., 8th Edition）Alkyl Halides from Alcohols

Conversion of Alcohols into Alkyl Halides Reactions with HX,SOCl2,PBr3

Conversion of Alcohols into Alkyl Halides Reactions with HX, SOCl2 , PBr3

Conversion of alcohol into a Leaving group Form Tosylate (p-TsCl,pyridine) Use strong acid (H3O+) Convert to Alkyl Halide (HX,SOC12,PBr3)

Conversion of Alcohol into a Leaving Group • Form Tosylate (p-TsCl, pyridine) • Use strong acid (H3O+ ) • Convert to Alkyl Halide (HX, SOCl2 , PBr3 )

Alcohols to alkyl Halides OH HX (HCI or HBr) +HOH rapid SN1 3 alcohol HX -X OH HOH moderate SN1 2°alcohol

Alcohols to Alkyl Halides OH 3 alcohol o HX (HCl or HBr) X + HO H rapid SN1 OH HX moderate S N1 X + HO H 2 alcohol o

Sy1:Carbocations can Rearrange B HBr cis trans

SN1: Carbocations can Rearrange HO HBr Br + Br cis & trans

HO Br D cis trans HO ⊕

HO H-Br Br + Br cis & trans HO H H - H2O Br Br

Lucas Test CH; CH3 ZnCl2 CH3COH CH:CCI forms is seconds 12M HCI CH3 CH3 HOZnC12 CH3 CH3 ⊕O CHC⊕ CI CH3 H CH3

Lucas Test C H3 COH CH3 CH3 ZnCl2 12M HCl CH3 CH3 C H3 CCl CH3 CH3 C H3 C OZnCl 2 H CH3 CH3 C H3 C C l forms is seconds + HOZnCl 2

Qualitative test for Alcohol Characterization OH CI primary >10 minutes (if at all) OH ZnC12,HCI secondary <5 minutes OH tertiary 1-2 seconds

Qualitative test for Alcohol Characterization OH primary OH secondary OH tertiary ZnCl2 , HCl Cl Cl Cl 1-2 seconds 10 minutes (if at all)

1 and 2 Alcohols:best to use SOC12,PBr3,or P/2 All are Sy2 Reactions S0C12 pyridine OH PBr3 P,I2 (in situ prep. ofPI3)

1 o and 2o Alcohols: best to use SOCl2 , PBr3 , or P/I2 OH SOC l2 pyridine PBr3 Br Cl P, I 2 I (in situ prep. of PI 3) All are SN2 Reactions

Thionyl chloride mechanism SOCh SO2 HCI pyridine

Thionyl chloride mechanism OH S O Cl Cl O H S O Cl Cl O H S Cl O O S Cl O - H+ Cl SOCl2 pyridine N C l + SO2 + HCl