What are  Hydrocarbons

Organic compounds containing only hydrogen and carbon are known as hydrocarbons. Hydrocarbons are divided into two main classes: aliphatic and aromatic. Aliphatic hydrocarbons are further divided into families: alkanes, alkenes, alkynes, and their cyclic analogs.
Alkanes or paraffins are saturated hydrocarbons with the general formula CnH2n+2. The principal source of alkanes are petroleum and natural gas.
Alkenes or olefins are unsaturated hydrocarbons having general formula CnH2n that contain the structural unit C = C . In alkenes, each doubly bonded carbon undergoes sp2 hybridisation and the three sp2 orbitals lie in the plane of carbon nucleus and are directed towards the corners of an equilateral triangle. The two doubly bonded carbon atoms lie in the same plane and there is a pi- electron cloud formed by lateral overlap of pz—pz orbitals lying above and below the plane of double bonded carbon atoms.
Main topics  of Alkenes
Alkenes-Bonding and nomenclature 
Isomerism in alkenes
Physical Properties of alkenes
Relative Stabilities of alkenes
Preparation of alkenes : Dehydration of alcohols
Alkyne family has a carbon-carbon triple bond as the functional group having the general formula CnH2n–2. In alkynes, the triply bonded carbon atoms use sp hybridised orbitals. For example, in acetylene (HC=CH), the carbon atoms use two sp hybridised orbitals to form two sigma bonds—sp-sp between carbon atoms and sp-s between carbon and hydrogen. The angle between the two orbitals is 180° giving a linear shape to the acetylene molecule. Each carbon has two p-orbitals containing 1 electron each. The lateral overlap of p-orbitals produces two pi-bonds which together make a single cylindrical sheath about the line joining the nuclei.

The Reimer-Tiemann reaction: Reaction and its Mechanism

Reimer-Tiemann Reaction Phenols on reaction with chloroform in the presence of sodium hydroxide (or potassium hydroxide) solution give hydro...