Chemistry: Haloalkanes and Haloarenes

Preparation of RX from ROH

ROH + HCl ——> RCl + H2O

Reagent: Anhydrous ZnCl2
ZnC

Preparation of RX from Phosphorus Halides with Alcohols

ROH + PCl5 ——> RCl + H3PO3

ROH + PCl3 ——> RCl + POCl3 + HCl

Preparation of RX from ROH using Thionyl Chloride

ROH + SOCl2 ——> RCl + HCl + SO2

Reagent: pyridine

Why is this preferred?

A: Byproducts are gasses, so pure component is obtained

Preparation of RX from alkane

RCH3 + X2 ——> RCH2X (and isomers) (presence of sunlight)

Why disadvantageous → formation of isomers, difficult to seperate

Iodination is reversible so addition of HIO3 (ox agent) to shift eqbln to right

Preparation of RX from alkene

RCH=CH2 + HX —> RCHX-CH3 (markonikov)

RCH=CH2 + HX —> RCH2-CH2X (anti markonikov, if benzoyl peroxide)

CH2=CH2 + X2 —> CH2X-CH2X (vicinal dihalide)

Finkelstein’s Reaction (obtaining Iodoalkanes)

R-X + NaI —> R-I + NaX

Reagent: Acetone

Swartz Reaction (obtaining Fluoroalkanes)

R-X + AgF —> R-F + AgX

(Freons - CFCs)

3CCl4 + 2SbF3 —> 3CCl2F2 + 2SbCl3

Preparation of Haloarenes from Arenes

Electrophilic Substitution

Aryl Fluorides can’t be made due to the high reactivity

Preparation of Haloarenes from Toluene

Large difference in MP of products so its easy to seperate

Sandmayer’s Reaction

Aniline has fishy odour