4.2.1/4.2.2 Alcohols and haloalkanes GapFill

Alcohols contain the functional group   OHNH2R(C=O)RCHO. This group is polar and, due to its ability to form  ionicdativehydrogenLondon bonds, gives alcohols greater water solubility and lower volatility than corresponding alkanes. Alcohols can be oxidised by heating with acidified potassium  dichromidedichrominedichromatedichromane(VI), K₂Cr₂O₇, solution, which is often represented in equations by [O]. Primary alcohols can be either partially oxidised to aldehydes, which have the functional group   CONH2CHOC=CCOOH, or fully oxidised to carboxylic acids, which have the functional group  R(C=O)RCOOHCONH2CHO. The extent of oxidation can be controlled by changing the experimental set-up. If the aldehyde is immediately distilled from the reaction mixture, it will not be oxidised further; if the reaction mixture is heated under   refugereflowrefletreflux, the major product will be a carboxylic acid. Secondary alcohols can be oxidised to ketones, which have the functional group   COOHC=CR(C=O)RCONH2 . Tertiary alcohols cannot be oxidised. Alcohols also undergo  reductionadditioneliminationsubstitution reactions in the presence of an acid catalyst, forming alkenes.

Haloalkanes are alkanes in which at least one hydrogen atom has been replaced by a halogen atom, represented by the letter X. Due to the high electronegativity of most of the halogens, C−X is a  triplemetallicpolardouble bond.

Nucleophiles are   carbon richcarbon deficientelectron deficientelectron rich, and have a lone pair of   moleculesprotonsneutronselectrons available to form a new covalent bond. One of the most important types of reaction that haloalkanes undergo is nucleophilic   combustiondecompositionsubstitutionaddition. Here, the nucleophile attacks the carbon atom in the C−X bond. At the same time, the C−X bond breaks, with both electrons moving to the halogen. The resulting halide ion is called the   departingleavingretreatingfleeing group.

Chlorofluorocarbons (CFCs) were once used in many industrial applications but have now been banned in most countries because they   require too much energy to makeare toxicsmell unpleasantdestroy the ozone layer.