General Organic Chemistry
1.0 Introduction
2.0 Classification of organic compounds
3.0 Homologous series
4.0 Nomenclature of hydrocarbons
4.1 The alkanes $(C_nH_{2n+2})$
4.2 The alkenes $(C_nH_{2n})$
4.3 The alkynes $(C_nH_{2n-2})$
4.4 Combined alkenes and alkynes
4.5 Cyclic hydrocarbons
5.0 Nomenclature of compounds containing halogens and nitro groups
6.0 Nomenclature of compounds with functional groups named as suffixes
6.1 Ethers and thioethers
6.2 Alcohols & thiols
6.3 Acids, salts of acids and acid anhydrides
6.4 Esters
6.5 Acid halides
6.6 Amides
6.7 Nitriles
6.8 Aldehydes
6.9 Ketones
6.10 Amines and ammonium salts
7.0 Nomenclature of aromatic compounds
7.1 Halogen and nitro-substituted aromatics
7.2 Carboxylic acids and derivatives
7.3 Phenols and thiophenols
7.4 Aldehydes & Ketones
7.5 Sulfonic acids and sulfonic acid derivatives
7.6 Aromatic amines
7.7 Diazonium ions $\left( {ArN_2^ + } \right)$
8.0 Radicofunctional naming
9.0 Organic reactions
9.1 Substitution or displacement reactions
9.2 Addition reaction
9.3 Elimination reaction
9.4 Rearrangement reactions
10.0 Electrophiles
11.0 Nucleophiles
12.0 Breaking and forming of bonds
13.0 Reaction intermediates
13.1 Carbocations
13.2 Carbanions
13.3 Carbon radical
13.4 Carbenes
13.5 Nitrenes
13.6 Arenium ions
13.7 Benzynes
14.0 Electron displacement effects
15.0 Inductive effects
16.0 Hyperconjugation
17.0 Resonance
18.0 Mesomeric effect
19.0 Electromeric effect
20.0 Inductomeric effect
21.0 Steric inhibition of resonance
22.0 Ortho effect
13.1 Carbocations
4.2 The alkenes $(C_nH_{2n})$
4.3 The alkynes $(C_nH_{2n-2})$
4.4 Combined alkenes and alkynes
4.5 Cyclic hydrocarbons
6.2 Alcohols & thiols
6.3 Acids, salts of acids and acid anhydrides
6.4 Esters
6.5 Acid halides
6.6 Amides
6.7 Nitriles
6.8 Aldehydes
6.9 Ketones
6.10 Amines and ammonium salts
7.2 Carboxylic acids and derivatives
7.3 Phenols and thiophenols
7.4 Aldehydes & Ketones
7.5 Sulfonic acids and sulfonic acid derivatives
7.6 Aromatic amines
7.7 Diazonium ions $\left( {ArN_2^ + } \right)$
9.2 Addition reaction
9.3 Elimination reaction
9.4 Rearrangement reactions
13.2 Carbanions
13.3 Carbon radical
13.4 Carbenes
13.5 Nitrenes
13.6 Arenium ions
13.7 Benzynes
An ion in which the carbon carries a positive charge is called carbocation.
They are formed by heterolytic cleavage.
Note: A carbocation is called primary $\left( {1^\circ } \right)$, secondary $\left( {2^\circ } \right)$ or tertiary $\left( {3^\circ } \right)$ when the carbon bearing the positive charge is attached to one, two or three alkyl (i.e. carbon) groups respectively.
Formation of carbocation
(a) By the addition of acids to
(i) Unsaturated compounds
(ii) Compounds containing oxygen atoms
(iii) Organic halides
(b) By the decomposition of diazonium salts
Reactions of carbocations
(a) Recombine with electron-rich species (electron pair of an ion or molecule).
(b) Eliminate a proton to form olefin
(iii) Rearrange to form more stable carbocation
(c) Add to alkene to form bigger carbocation
Geometrical shape: The carbocation takes up the more stable $sp^2$ configuration with the vacant $2p$ orbital at right angles to the plane of the $sp^2$ orbitals.
Stereochemical effect: The vacant $2p$ orbital can be attacked from either side of the plane of the ion by an electron-rich species. This may result in the formation of both the optical isomers in suitable substrates.