What topics to review before starting organic chemistry?
As @inɒzɘmɒЯ.A.M pointed out in his comment, the usual prerequisite for an organic chemistry course is that a general chemistry course is already taken and successfully passed. The general chemistry is, of course, a rather large topic, so I'll just name a few subtopics which I feel are absolutely essential to start a venture into the world of organic chemistry.


Structure of matter.


Modern atomic theory (Schrödinger equation, atomic orbitals, spin,  Pauli exclusion principle, electron configurations).
The periodic table (periodicity, group trends).
Chemical bonding (covalent and ionic bonding, Lewis structures, resonance, VSEPR theory , introductory Valence Bond Theory and Molecular Orbital Theory).

Chemical reactions.


Nomenclature &amp; stoichiometry (empirical and molecular formulas, chemical equations, mole, limiting reagents, yield).
Solutions (solubility, concentration, properties of solutions).
Acid-base reactions (definitions of acids and bases, pH, strong/weak acids and bases, trends).
Oxidation-reduction reactions (oxidation numbers, balancing oxidation-reduction reactions).

Thermodynamics.


Basic concepts (energy, work, heat, enthalpy, entropy, Gibbs free energy ).
The first and the second laws of thermodynamics.
Hess's law.

Kinetics.


Reaction rates (temperature dependence, Arrhenius equation).
Reaction orders (first and second order reactions, molecularity, rate laws).
Catalysis.

Chemical equilibrium.


Basic principles (the notion of equilibrium, the law of mass action, equilibrium constants, the direction of a reaction).
Shifting the equilibrium (changing amounts, pressure, volume, temperature).