haloalkanes Flashcards
Alkyl Halides
derivative of alkane by replacing one hydrogen atoms by halogen atom. Monohalo derivative.
ethylidene chloride’s formula
1, 1- Dichloroethane geminal dihalides
ethylene dichloride’s formula
1, 2-Dichloroethane vicinal dihalides
what is the product when we react alcohol with HX ?
RX + Water
What is the product when alcohol reacts with HX according to SN1 mechanism?
water gets loss and carbocation is formed (rearrangement if possible) in the first step. In the second step Halide ion reacts over it and we get alkyl halide.
what is the product when alcohol reacts with HX according to SN2 mechanism?
It is a single step reaction so we directly get our products RX and water.
How are phosphorus halides prepared?
red Phosphorus + Halogens
what is the advantage of using phosphorus halides?
carbocations are not formed so no possibility of rearrangement in prior of forming products. so no SN1 mechanism
ROH + PCl 5 =
RCl + POCl 3 + HCl
3ROH + PCl 3 =
3RCl + H 3 PO 3
3ROH + PBr 3=
3RBr +H 3 PO 3
3ROH + PI 3=
3RI + H 3 PO 3
what is the product when alcohol reacts with Thionyl Chloride SOCl 2? ( in the presence of pyridine) and what is the use of pyridine over here?
R-Cl + SO 2 +HCl both are gaseous products so they can escape. Pyridine is used to trap HCl gas so as to form pyridinium chloride. The products are formed with inversion of configuration in presence of pyridine (SN2) and retention of configuration in absence of Pyridine(SN1).
Direct halogenation of Hydrocarbon in presence of U.V light gives? which Halogens are most reactive and least reactive ? which degree hydrogen would replace first? and which Last?
RX +HX.
F 2
I 2
Tertiary hydrogen then secondary hydrogen and then primary hydrogens.
what measures are taken while halogenating with I 2 ?
I 2 is reversible so we use oxidizing agents to oxidize HI formed by HIO 3 or HNO3