halogen derivatives

substitutive names

prefix of a halogn and the name of a hydrocarbon

-ine -> -o

more atoms of the same halogen - greek numerical prefix

radicofunctional names

hydrocarbyl followed by the name of a halogen

trivial names

non-systematic names

no indication to chemical structure

Z-isomer

atoms with higher priorities are on the same side of the double bond

E- isomer

Higher priority groups on opposite sides.

Stereoisomers

Compounds with the same structural formula but with a different arrangement of the atoms in space

E/Z isomerism

requirement for at least two different atoms to be attached to each C atom of the C=C bond

classification of halogen derivatives

primary secondary tertiary quarternary

electronic displacement

occurs when electrons move toward one side or part of a molecule

responsible for reactivity

cause permanent polarisation of the bond

inductive effect

covalent bond is formed between atoms of different electronegativity, the electron density is more towards the more electronegative atom of the bond

results in a polar covalent bond

polar C-Cl bond

induces polarity in the adjacent bonds

substituents are classified as

electron-withdrawing and electron-donating groups

negative inductive effect

atoms which are more electronegative than carbon

decrease electron density

electron acceptors

->Cl<-

Positive inductive effect

atoms with have lower electronegativity than carbon atoms

increase electron density

electron donors

<-Zn->

Resonance Effect

the polarity produced by the interaction of two pi bonds or between a pi bond and a lone pair of electrons

transmitted trough the chain

results in a different distribution of electrons

positive resonance effect

transfer of electrons away from the substituent group attached to the hydrocarbon (reorganization of the double bonds)

Negative resonance effect

transfer of electrons towards the substituent group

(double bonds are reorganized and the substituve group gains a bond)

haloalkanes

halogen is bonded to a sp3 hybridised C atom

haloarenes

halogen is bonded to an sp2 hybridized C atom of a benzene

state of matter

lowest halogen derivatives are gases, higher are liquids or solids

density

density increases down the group

R-I > R-Br > R-Cl > R-F

colour

colourless when pure, Br and I develop color when exposed to UV

melting/boiling points

higher than those of corresponding hydrocarbons due to a higher molecular mass

boiling point decreases with branching

stability

F>Cl>Br>I

nucleophilic substitution reactions

C atom acquires a partial positive charge

Halogen atom acquires a partial negative charge

C atom is prone to get attacked by nucleophilic reagents

C and nucleophile bond

halide ion gets removed

reactivity

I>Br>Cl>F iododerivatives are the most reactive

reaction with aqueous alkali

An alcohol is produced when a halogenoalkane reacts with an aqueous alkali, like KOH.

elimination reaction

removal of molecules leading to the formation of double or triple bonds

alpha carbon

C atom carrying the halogen

beta carbon

carbon bonded to the alpha carbon

beta hydrogen

A hydrogen atom directly bonded to a β-carbon.

Dehydrohalogenation

alkyl halides with beta hydrogen are heated with a base the halogen is eliminated from an alpha position and a hydrogen from beta position leading to the formation of alkenes

Saytzeff's Rule

when two or more alkenes can be produced in an elimination reaction the thermodinamivally most stable one is the major product

organometallic compounds

metal atom is directly bonded to a carbon atom

grinards reagents

compounds of Mg with alkyl and aryl halides

ecological poisons

halogen derivatives burden the enviroment because they are not naturally degraded in nature

trichloromethane/chloroform

non-flammable, volatile liquid with a sweet smell

carcinogenic effect

pest control agents

oxidized by air in the presence of UV to form poisonous phosgene

DDT

used to control malaria, but its use has been banned

freon-12

non flammable gas used as a propellant in sprays