Ch 3Haloalkanes and Haloarenes — Class 12 Chemistry, concept-first.

Organic compounds in which one or more hydrogen atoms of a hydrocarbon are replaced by a halogen atom (fluorine, chlorine, bromine or iodine) are called organohalogen compounds.

Fluorine, chlorine, bromine and iodine are all more electronegative than carbon, so in every haloalkane the bond is a polar covalent single bond with the carbon carrying a partial positive charge and…

Boiling points. Haloalkanes have distinctly higher boiling points than the alkane of the same carbon skeleton.

The mechanism (Substitution, Nucleophilic, Bimolecular) is the pathway by which primary haloalkanes, and to a lesser extent secondary ones, react with good nucleophiles.

The mechanism (Substitution, Nucleophilic, Unimolecular) dominates for tertiary, and for benzylic or allylic, haloalkanes reacting under conditions of a weak nucleophile and a polar protic solvent.

Predicting whether a haloalkane will react by or requires weighing three factors together -- the substrate's structure, the nucleophile's strength, and the solvent -- rather than any one of them in is…

A carbocation is a carbon bearing only three bonds and a formal positive charge, with an empty orbital; it is -hybridised and planar at that carbon.

A carbon is a stereocentre (chiral centre) when it carries four different groups; such a carbon and its mirror image are non-superimposable, giving rise to a pair of enantiomers.

Before the CIP system was developed, chemists described the configuration of a stereocentre relatively, by comparing it to an arbitrarily chosen reference compound rather than by any absolute priority…

In a haloarene, the halogen is bonded to a ring carbon that is -hybridised and part of the ring's continuous, conjugated system.

A halogen substituent on a benzene ring shows a combination of electronic effects unusual among ring substituents: it deactivates the ring towards electrophilic substitution (making the reaction slowe…

Several simple polyhalomethanes are produced and used industrially, and some have important -- occasionally sobering -- histories in medicine, alongside genuine, well-established hazards that govern h…

Freons is the trade name for a family of chlorofluorocarbons (CFCs) -- simple haloalkanes bearing only fluorine and chlorine on a short carbon chain, of which Freon-12 (, dichlorodifluoromethane) is t…

DDT -- systematically p,p'-dichlorodiphenyltrichloroethane, and more fully 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane -- was the first synthetic organochlorine insecticide to see widespread use.

Sample papers and previous-year board questions for this subject.