Organic Chemistry Review Sn1, Sn2, E1, E2 Reactions

Organic Chemistry may have a bad reputation,,, but its actually quite simple. Something I notice alot of students struggle with in Ochem 1 is Sn1, Sn2, E1 and E2 reactions.
First off, Lets define two types of reactions, A) substitution reactions and B) Elimination reactions
Substitution reactions occur when an Alkyl Halide reactes with a nucleophile in a way that the nucleophile replaces the halogen attatched to the carbon strand/ring.
Substitution reactions can be split into two groups: A) Sn1 reactions and B)Sn2 reactions
Things to remember about Sn1 reactions:
1) Sn1 reactions are two step reactions, meaning the bond breaks between the carbon and the halogen, and afterward the nucleophile attatches itself to the positive carbon(electrophile). Because there is an intermediate product (the carbon strand without the halogen) the stability of this itermediate product will determine the speed of the Sn1 reaction. Stability of the intermediate product is determined by how many R groups are attatched to it, meaning a tertiary alkyl halide will definatly go through an Sn1 reaction, while a secondary alkyl halide may go through an Sn1 reaction, and a primary alkyl halide will not go through an Sn1 reaction.
2)The Sn1 reaction results in a racemic mixture as its product.
3)The Sn1 reaction exhibits first order kinetics, meaning that only the concentration of the alkyl halide effects the rate of reaction (concentration of nucleophile has no effect)
4)favored by polar protic solvents
Things to remember about Sn2 reactions:
1)The Sn2 reaction is a one step reaction meaning that the bond between the halogen and carbon breaks as the bond between the nucleophile is created. Because of this, limiting steric strain will speed up the Sn2 reaction. If the nucleophile is “bulky” the reaction will be too slow, and if the alkyl halide is bulky, the reaction will not start. For Sn2 reactions, primary alkyl halides are the best candidates for Sn2 reaction, secondary alkyl halides can go through Sn2 reactions, and tertiary alkyl halides do not go through Sn2 reactions.
2)The stereochemistry of an Sn2 reaction is very specific in that the nucleophile always attacks from the opposite side of the halogen. This results in the inversion of configuration at a stereogenic center.
3)The Sn2 reaction exhibits second order kinetics, meaning that the concentration of the alkyl halide and the nucleophile both effect the rate of reaction. If you double concentration of both, you quadruple you reaction speed.
4) favored by polar aprotic solvents
Elimination reactions occur when a base attacks a hydrogen attatched to a carbon which is diagnal from the halogen. After the hydrogen leaves, the carbon forms a double bond with a the carbon bonded to the halogen, which in turns releases the halogen.
Elimination Reactions can be split into two groups:A)E1 Reactions, B)E2 Reactions
Things to remember about E1 reactions
1) similar to Sn1 reactions, E1 reactions are a two step reaction, and exhibit first order kinetics in the same fashion.
2)Weak bases favor the E1 reaction.
3)more substituted halides react fastest, meaning tertiary alkyl halides react the fastests, while primary halides rarely react, (if at all)
4)Polar protic solvens that solvate the ionic intermediates are needed
Things to remember about E2 reactions
1) similar to Sn2 reacitons, E2 reactions are a one step reaction, and exhibit second order kinetics in the same fashion
2)Strong Bases favor the E2 reaction
3)more substituted halides react fastest, meaning tertiary alkyl halides react the fastests, while primary halides rarely react, (if at all)
4) favored by polar aprotic solvents

Precipitation Reactions

A precipitations reaction is a reaction where a precipitate (or solid) forms upon mixing two solutions.

Here is a video of a precipitate reaction

You can predict the result of a precipitation reaction by understanding that only insoluble compunds will form a precipitate. If the precipitation reaction is between two solutions containting soluble compounds, the two compounds will combine.

Chemistry -Limiting Reactant, Theoretical Yeild, and Percent Yeild

The Limiting Reactant– this is the reactant which is completely consumed in a chemical reaction. It limits your reaction therefore limiting the amount of product.

The reactant in excess– This is any reactant in which you have a quantity greater thant that required to completey react with the limiting reactant

The theoretical yeild– this is the amount of product than can be made in a chmeical reaction based on the amount of limiting reactant, this is a theoretical data figure.

The Actual Yeild– This is the amount of product actually produces by your reaction, this data is always from a physical test.

The percent yeild– this is the difference between the actual yeild and the theoretical yeild. generally the figure is given as a percent in which case you would multiply it by 100

Chemical Bonds

Here are a couple chemical bonds, and their descriptions.

Ionic Bonds: This is when a metal and a non metal ineract. During this interaction, the metal transfers one or more of its electrons to the non-metal. After the metal loses its electron(s) it becomes positively charged, and the non metal becones negatively charged. The term for the positively charged atom is cation while the negatively charged atom is refered to as an anion.  The oppositely charged ions are attracted ti each other by electrostatic forces, and this is called an ionic bond. molecuels which were formed by an ionic bond are refered to as ionic compunds.

Covalent Bond: A covalent bond occurs between two non-metals. In this scenario neither of the atoms loses its electron, and neither atoms gains the other’s electron. Rather, the two atoms “share an electron.” The reason why the non-metal atoms do this is because all non metals want to increase the amount of electrons they have to become like one of the noble gases, in contrast to metals who want to lose electrons to become similar to a one of the noble gasses. The non-metals split the electron which will rotate around both atoms which will in turn keep the atoms together. A group of atoms strung together with this type of bond is called a molecular compound.

Moles, and molarity

Ok so yes this is very basic but I am just going to review what a mole is and what molartiy is.

First off 1 mole is a number and it is equal to 6.022*10^23 atoms.

The magic of this number is that the mass of a mole of some particular molecule is equal to its molecular weight, so 1 mole of O2 equals 32g.

Molarity is usually used for a solution, and the units of molarity are usually Moles/liter, (or some mole/volume)

so if there were 1 moles of some molecule in 3 L of water the Molarity would be 1/3 or .333333 moles/L

Chemistry–The Periodic Table of the Elements