Carbon and its Compounds

Covalent bonding in carbon, homologous series and functional groups, naming, and the reactions of ethanol and ethanoic acid; soaps and detergents.

Key ideas

Carbon forms covalent bonds by sharing electrons, because gaining or losing 4 electrons is too hard.
Carbon has a valency of 4 and joins to other carbon atoms in chains, branches and rings (catenation).
A homologous series has the same functional group, and each member differs from the next by CH₂.
Saturated compounds have only single bonds; unsaturated ones have a double or triple bond.
Names: meth- (1 carbon), eth- (2), prop- (3), but- (4); endings -ane, -ene, -yne, -ol, -al, -one, -oic acid.
Reactions: combustion, oxidation (ethanol to ethanoic acid), addition of hydrogen to unsaturated compounds (nickel catalyst), and substitution with chlorine in sunlight.
Soap molecules form micelles that trap oil; soap forms scum in hard water, detergents do not.

Alkanes / alkenes / alkynes	C_nH_2n+2 / C_nH_2n / C_nH_2n−2
Ethanol / ethanoic acid	C₂H₅OH / CH₃COOH
Functional groups	alcohol –OH, aldehyde –CHO, ketone >C=O, carboxylic acid –COOH
Esterification	CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O (acid catalyst)

For ethane (C₂H₆), how many C–H bonds and carbon–carbon bonds of each kind are there? How many covalent bonds (shared pairs) in all?

Working: a double bond is 2 shared pairs, a triple bond 3

Answer: C–H: 6; C–C single: 1; 7 shared pairs