Halo Alkanes And Arenes

Question 1

Total method of prep of haloalkanes

Answer 1

3
1) from alcohol
2) from hydrocarbon
3) from halogen exchange

Question 2

Prep of haloalkane from alcohol
Rexn with halogen acid

Answer 2

By rexn with HCl in presence of ZnCl2
By rexn of alcohol with NaBr and H2SO4 to give RBr and NaHSO4 with H2O

Question 3

Prep of haloalkane from alcohol
Rexn with phosphorus halides

Answer 3

By rexn of alcohol with PX3 to give RX and H3PO3
By rexn of alcohol with PCl5 to give RCl and POCl3 and HCl

Question 4

Prep of haloalkane from alcohol
Rexn with red phosphorus

Answer 4

ROH + red P/X2 gives RX

Question 5

Prep of haloalkane from alcohol
Rexn with thionyl chloride/Darzens process

Answer 5

ROH+SOCl2 gives RCl and SO2 and HCl

Question 6

Prep of haloalkane from hydrocarbon

Answer 6

1) from alkane by free radical halogenation
2) from alkens(by add of hydrogen halides and by addition of halogen)

Question 7

Prep of haloalkane from alkane by free radical halogenation

Answer 7

Reagent Cl2/UV light or heat
Gives mixture of mono and poly haloalkane isomers

Question 8

Prep of haloalkane from alkens

Answer 8

By rexn with HX

By addition of halogen
Alkene + Br2 gives vicinal di bromide
Reagent is CCl4

Question 9

Prep of haloalkane from halogen exchange

Answer 9

Finkelstein
Swarts

Question 10

Finkelstein

Answer 10

Add of iodine

RX + NaI in presence of dry acetone to give RI +NaX

Question 11

Swarts

Answer 11

Alkyl fluoride
R+Metal fluoride give alkyl fluoride+halogenMetal
Ex RBr+AgF give RF + AgBr

Question 12

Prep of haloarene

Answer 12

1) by hydrocarbon by ESR
2) from amine by sandmeyer

Question 13

Prep of haloarene by esr

Answer 13

Tolune+X2 in presence of dark + Fe gives O-halotoluene and p-halotoluene

This rexn takes place in presence of Lewis acid catalyst like iron or iron3chloride

Question 14

How can ortho and para isomer of haloarene can be seperate

Answer 14

Due to large difference in their melting point

Question 15

Rexn with iodine by esr to prep haloarene

Answer 15

Can be reversible and require presence of an oxidising agent (HNO3 and HIO4) to oxidisd HI formed during iodination

Question 16

Are fluro compounds prepared by esr for prep of haloarene

Answer 16

No
Due to high reactivity of fluorine

Question 17

Prep of haloarene from amine by Sandmeyer

Answer 17

Prep of diazonium salt
Primary aromatic amine in presence of NaNO2 and HX at 273-278K give benzene diazonium salt

Benzene diazonium salt with cuprous chloride Or cuprous bromide (Cu2X2) give arylhalide and N2
Where halogen=Cl, Br

Question 18

Replacement of the diazonium grp by iodine to prep haloarene

Answer 18

Do not require presence of Cu2X2 and is done simply by shaking the diazonium salt with potassium iodide

Question 19

Elimination rexn of haloalkane/B elimination

Answer 19

Reactant-Haloalkane with B hydrogen atom
Reagent-alcoholuc solution of Pottasium hydroxide (KOH) give Alkene+HX

Question 20

Zaitsev rule

Answer 20

Given by Alexander zaitsev
In dehydrohalogenation (B elimination)
The preferred product is that alkene which has greater no of alkyl grp attached to the double bonded carbon atoms

Question 21

Rexn of haloalkane with metals

Answer 21

Reagent-DE
Gives RMgX (Grignard reagent)

Question 22

Organo mettalic compound

Answer 22

Compounds containing carbon metal bond

Question 23

Wurtz rexn

Answer 23

In presence of DE
In products no of C is double
2RX+2Na in Dry ether gives RR and 2NaX

Question 24

Why aryl halides are extremely less reactive towards SN rexn

Answer 24

1) due to resonance
2) diff in hybridization of C in haloalkane and haloarene
3) instability of phenyl cation
4) because of repulsion

Question 25

Replacement by hydroxyl grp by haloarene/Dow’s process

Answer 25

Chlorobenzene to phenol in presence of NaOH 623K 300atm and H+

In presence of NO2 at ortho and para position
1) 1 NO2 temp-443K
2) 2 NO2 temp-368K
3) 3NO2 warm H2O

No effect on electronegative of haloarene for ewg at meta

Question 26

ESR of Haloarene

Answer 26

1) Halogenation
Reagent-Anhyd FeCl3

2) Nitration
Reagent-HNO3 and Conc H2SO4

3) sulphonation
Conc H2SO4

4) Friedel craft rexn
a) CH3Cl and anhydrous AlCl3
b) CH3C(=O) Cl and anhydrous AlCl3

Major product-para position
Minor-ortho

Question 27

Wurtz fitting

Answer 27

Aryl halide and alkylarene in presence of Dry ether and sodium

Question 28

Fitting rexn

Answer 28

2Arylgrp +2Ba in presence of dry ether give Diphenyl+2NaX