The way organic reactions happen can change a lot based on certain conditions. This is especially true for reactions like nucleophilic substitution, elimination, and addition. Here are some important factors to consider:

1. Temperature:

   • When the temperature goes up, the energy of the reactants usually increases too.
   • This helps the reactions happen faster.
   • For example, if you raise the temperature by 10°C, the reaction rate can double. This idea comes from something called the Arrhenius equation, which shows how temperature affects reaction speed.

2. Solvent:

   • The type of solvent you use can change how a reaction works.
   • Polar protic solvents (which have a certain structure) tend to stabilize ions and often promote SN1 reactions.
   • On the other hand, polar aprotic solvents usually support SN2 reactions because they create less blocking around the reactants.
   • For instance, an SN2 reaction can happen a lot faster in acetone (which is polar aprotic) than in water (which is polar protic).

3. Concentration of Reactants:

   • How much of each reactant is present also matters.
   • In an SN2 reaction, the speed depends on the amount of both the nucleophile (the attacking particle) and the electrophile (the target particle). This means that if you increase their amounts, the reaction will go faster.
   • Typically, the concentration of a nucleophile in an SN2 reaction is between $0.1$ and $1.0 \, \text{mol/dm}^3$.

4. Presence of Catalysts:

   • Catalysts are substances that help reactions happen more easily. They lower the energy needed for a reaction to occur.
   • For example, enzymes are catalysts that can make reactions happen much faster.

Each of these factors can change how an organic reaction takes place. This shows why it’s important to find the best conditions for reactions in the field of synthetic organic chemistry.