1. Haloalkanes and Hydroxide Ions
SN1 AN SN MECHANISM
Haloalkanes and Hydroxide Ions

2. SN1 Reaction- Introduction
The Sn1 reaction is a substition reaction in organic chemistry. Sn stands for nucleophilic substitution and “1” represents the rate-determining step is unimolecular. An examole of a reaction taking place with an Sn1 reaction mechanism is the hydrolysis of tert-butyl bromide with water forming tert-butyl alcohol.

3. SN1 Reaction- 1
Step1…. Formation of a tert-butyl carbocation by seperation of a leaving group from the carbon atom and it is slow and reversible.
Step 2…. The carbocation reacts with the nucleaophile and if nucleohile is a neutral molecule, a third step is required to complete the reaction, this reaction step is fast.

4. SN1 Reaction- 2
Step 3…. Deprotonation- Remoe a proton on the protonated necleophile by water acting as a base forming the alcohol and a hydronium ion. The reaction steps is fast.

5. Addition
Sn1 reactions take place in two steps excluding protonation or deprotonation. The rate determining step is the first step, so the rate of the overall reaction is essentially equal to that of carbonation formation and does not involve the attacking nucleophile. Thus nucleophilicity is irrelevant and the overall reaction ratedepends on the concentration of the reactant only. Two common side reactions are elimination reactions and carbocation rearrangement.

6. SN1 Reaction - Animation

7. SN2 Reaction- Introduction
The Sn2 reaction is known as bimolecular nucleophilic substitution where a lone pair from a nucleophie attacks an electron deficient electrophilic center and bonds to it and expelling a leaving group.

8. SN2 Reaction Mechanism
The reaction most often occurs at the carbon center with an electronegative, stable leaving group attached to the halide atom. The breaking of the C- X bond and the formation of the new C-Nu bond occur to form a transition state. The leaving group is pushed off the opposite side and the product is formed by the necleophile attacking the carbon.
In the Sn2 reaction, the attack of OH on a bromoethane results in ethanol with bromide ejected as the leaving group.

9. SN2 Reaction - Animation
CH3Br + CN- → CH3CN + Br-

10. Conclusion
Sn1 and Sn2 reaction are nucleophilic substitution reactions in the positive charged species attract and form week electrostatic bonding.
Sn1 only work with secondary or teritary carbocations because the carbocations must be stable, neighboring groups are present that can donate electron density into the carbocation to help stabilize it.
Sn2 only work on primary or secondary carbons, a carbocation is not formed. As a nucleophile approaches the target carbon atom, it begins to form a bond with the carbon. At the same time, the carbon atom begins to lose it's bond with the leaving group.