Jodi-Ann Fletcher

R-XX- F, Cl, Br, I

Usuallly colourless Immiscible in water Denser than water Held mainly by VAN DER WAALS

FORCES Has permanent dipole dipole attraction

to smaller extent As chain length increases (VDWForces

increases), solubility decreases and boiling point increases

Primary- contains one alkyl group

Secondary- contains two alkyl groups

Tertiary- contains three alkyl groups

Halogen atoms more electronegative than carbon atoms

C-X polar C atom of C-X more prone to

nucleophilic attack. Halgoneoalkane saturated (all bonds

filled) Halogenoalkanes therefore undergo

nucleophilic substitution

Two types: unimolecular and biomolecular substitution

Unimolecular(SN1)- one concentration determines rate of reaction

Biomolecular (SN2)- two different concentrations determine the rate of reaction

Two stages Step1: heterlytic bond fission of C-X

bond to give carbocation and X- due to repulsion of electron density to X with nucleophile.

Step 1 is the rate determine step Step 2: Carbocation combines with

nucleophile.

Rate of rxn proportional to conc of Nucleophile

Nucleophile attacks C of C-X Transition compound formed The X captures all the two electrons of

C-X The above is the slow stage Then the nucleophile and Carbocation

are still joined Then a part of nucleophile, the more

positive end attracted to X- andtwo compounds form

Primary halogenoalkanes undergo Sn2 reactions

Tertiary halogenoalkanes undergo SN1 reactions

Secondary halogenoalkanes undergo both SN1 and SN2 reactions.

Reaction with water very slow at room temperature

Reaction can be brought about in vapour stage (as steam)

Products are alcohol and hydrogen halide

In alkaline conditions, reaction rapid

Nucleophile water causes repels electron density towards X of C-X bond

Heterolytic splitting of C-X bond Carbocation and X- form Water gives a lone pair to carbocation Hydrogen atom is removed from water

compund to X-

Alcohol and hydrogen halide form

Nucleophile water attacks slightly positive C atom in C-X bond

Nucleophile donates lone pair while X is ejected with electrons in C-X bond

Water then X- quickly accept the proton from protonated alcohol

Alcohol and HX form.

Cnditions: dilute NaOH under reflux

Nitrile formed Conditions: ethanol solvent, heat under

reflux CN and nitriles used to increase length

of C chain in organic synthesis Nitrile can then be converted to other

products such as nitrile

General formula: R-X + CN- R-CN + X-

Eg CH3Br+NaCN CH3CN + NaBr Possible further conversion to amine

RCN + 4[H] RCH2NH2

Conditions: NaBH4 and ether

CN can then be hydrolysed to form carboxylic acid

R-X + CN- R-CN + X-

To RCN+2H2O + H+Cl- RCO2H + NH4

+Cl-

Conditions: heat in reflux with dil. Strong acid

Eg CH3CN+H2O+ HCl CH3COOH + NH4Cl

R-X + H-:NH2 R=:NH2+ HX Eg C2H5Br+ NH2 C2H5NH2+ HX Amine formed But with excess R-X, further substitution

occurs Until N no longer has a lone pair, has

four bonds. Eg C2H5Br+ (C2H5)3N (C2H5)4N+Br-

From alcohols by substituting HX From alkanes by substituting HX From alkenes for adding HX