Drawing Mechanisms Quiz: Leaving Groups and Reaction Kinetics

Study Notes

Types of Reactions

Addition, Elimination, Substitution, Condensation, Oxidation, and Reduction reactions are types of reactions that have been studied.

Reaction Mechanism

A reaction mechanism is the step-by-step sequence of elemental reactions by which a chemical change occurs.
It shows the movement of electrons to make and break bonds.
Mechanisms can be categorized into two main categories: Attack of a nucleophile and Attack of an electrophile.

Drawing Mechanisms

Steps to drawing mechanisms:
- Decide if the reagent is a nucleophile or electrophile.
- Identify areas of partial charge on the substrate that the electrophile or nucleophile may attack.
- Draw a curly arrow between the nucleophile/electrophile and the substrate.
- Consider whether a bond needs to be broken to make a stable intermediate.
- Choose the best bond to break and draw a curly arrow.
- Draw the product made by moving these electrons.
- Account for all the atoms in the reactants and check the overall charge.
- Decide if the reaction is complete or if an intermediate has been made.
- Repeat the process until a stable product is formed.

Curly Arrows

Curly arrows show the movement of electrons.
Arrows go from the area of negative charge to the area of positive charge.
A full arrowhead shows the movement of a pair of electrons.
Curly arrows should be curved, not straight.

Bond Counting

Each element forms a standard number of covalent bonds: Hydrogen (1), Oxygen (2), Nitrogen (3), Carbon (4).
Nitrogen and oxygen can temporarily form extra bonds.
If an extra bond is made to carbon, another bond must break.
To break a bond, draw a curly arrow from the bond to the more electronegative atom.

Leaving Groups

The best leaving groups are neutral molecules or large and electronegative elements (e.g., H2O, I-, Br-).
Good leaving groups: F-, -OH, -C≡CH, -NH2, -H, -CH3.
Bad leaving groups: None specified.

Drawing Products

Draw the product made by moving electrons.
Account for all the atoms in the reactants and check the overall charge.

Conservation of Matter

Matter (including electrons) cannot be created or destroyed.
The number and type of atoms must be equal on both sides of the reaction arrow.
The overall charge must be equal on both sides of the reaction arrow.

SN1 Reactions

SN1 is a nucleophilic substitution reaction with one species in the rate determining step.
SN1 reactions occur with tertiary haloalkanes.
The most stable carbocation intermediate is the one with the most alkyl groups substituted.

Carocation Stability

Order of stability: tertiary (3°) > secondary (2°) > primary (1°).
Stability increases with the number of alkyl groups substituted.

SN1 or SN2

Tertiary haloalkanes undergo SN1 reactions because tertiary carbocations are the most stable.
Primary haloalkanes undergo SN2 reactions because primary carbocations are the least stable.
Secondary haloalkanes undergo a mixture of SN1 and SN2 reactions.

Description

Test your knowledge on leaving groups and drawing mechanisms in organic chemistry. Learn about the characteristics of good and bad leaving groups, how to draw partial charges, and the steps involved in drawing reaction mechanisms.