Singly bonded functional groups

What are two examples of common alkyl halides?

PVC and CFCs

What is the reagent used to synthesis alkyl halides from alkenes?

HBr

What is the reagent used to synthesis alkyl halides from alcohols?

SOCl or PB3

Is a large atom a better or worse leaving group?

Better

Where do alkyl halides undergo Nucleophilic attack and what does this result in?

At the carbon atom. Results in a pentavalent carbon so another bond must break at the same time

What are nucleophiles and what are some examples?

Negatively charged or neutral species (NH3, H2O, Br-, OH-)

What are electrophiles and what are some examples?

Positively charged or neutral species (C=O, BF3, H+, NO2+)

How to go from an alkyl halide to to a primary amide (forms a C-C bond)

Nucleophilic substitution using CN- to form a nitrile and then reduce using LiAlH4

What is retrosynthesis?

Starting with the products and working backwards to find the starting materials

How to form a C-C bond using an alkyne?

1. Deprotonates the alkyne (use NH2+ from NaNH2).

2. The anion acts as a nucleophile on the alkyl halide and does Nucleophilic substitution

How to form primary alkyl amides with a nitrogen based nucleophile (number of carbons stays the same)?

1. Form the alkyl azide

2. Reduce using LiAlH4

Steps of the William ether synthesis?

1. Deprotonate the alcohol to form the nucleophile

2. Nucleophilic substitution of the nucleophile with the alkyl halide to form the ether

What is the finkelsteim reaction?

Useful for preparing alkyl iodides. Nucleophilic substitution.

Sn1 steps?

1. halogen leaves the nucleophile

Nucleophile attaches the carbocation (Front or back attack)

What is the rate equations for Sn1 mechanisms?

Rate = k[Rx]

What alkyl halides undergo Sn1 mechanisms?

Usually tertiary (sometimes secondary). Sn1 favours groups which give stable carbocations.

Stereochemistry implications of Sn1 mechanisms?

Not stereo specific. If it has a chiral centre, both enantiomers can be formed.

What is a racemic mixture?

50-50 ratio of the enantiomers

Sn2 steps?

1. Nucleophile attacks the electrophilic carbon

2. Forms a transition state

3. Leaving group is kicked out at the same time

What is the rate equations of Sn2 mechanisms?

Rate = k[Rx][Nu]

What alkyl halides undergo Sn2 mechanisms?

Usually primary (sometimes secondary). Not favoured by bulky substrates

What are the stereochemical implications of Sn2 mechanisms?

Always forms the inverted molecule

Can there be Sn2 reactions at a carbon with Sp2 hybridisation?

No

Sn1 mechanisms are favoured by which solvents?

Polar protic solvents (stabilises the carbocation by solvation)

What are some examples of polar protic solvents?

Water, methanol, ethanol, ammonia, acetic acid

What are polar protic solvents?

Liquids that have a partial positive hydrogen atom (due to being bonded to a highly electronegative atom)

SN2 mechanisms are favoured by which solvents?

Polar aprotic solvents (dissolve ionic nucleophiles but don’t solvate them = keeps the nucleophile reactive)

What is a polar aprotic solvents?

A molecule that is polar but lacks a hydrogen atom directly bonded to an electronegative atom

Examples of polar aprotic solvents?

Dimethyl sulfoxide (DMSO), acetone, DMF

Why do elimination reactions compete with Nucleophilic substitution reactions?

Because bases and nucleophiles are similar.

What are the 3 factors to determine whether a reaction undergoes E1 or E2 mechanism?

The base (strong = E2, weak = E1), the solvent (polar protic = E1, not important in E2), the alkyl halide (primary = E2 but can do all three, tertiary = E1 and can only do 2 and 3)

Stereospecific requirements of E2 reactions?

The leaving group must be anti to the hydrogen removed (anti-periplanar). Must be on opposite sides.

If there is an unsymmetrical alkyl halide what is formed?

Two products. The major product is the alkene that is more highly substituted at the double bond because it is more stable (zaitsev’s rule)

Sn1/Sn2 vs E1/E2 outcomes for primary alkyl halides?

Sn2 with a good nucleophile. E2 with a strong, sterically hindered base.

Sn1/Sn2 vs E1/E2 outcomes for tertiary alkyl halides?

E1 in the presence of a base

In a finkelstein reaction, what does the KX product need to be?

Insoluble

What does an epoxied + nucleophile form?

A diol

Are alkoxides good bases in E2 reactions?

Yes

What does the hydration of alkenes form?

Alcohols

Do primary, secondary and tertiary alcohols dehydrate easily?

Primary and secondary do not. Tertiary dehydrate easily to form alkenes.

Are ethers reactive?

Usually not (often used as solvents)

What are epoxides (aka. Oxiranes)?

Three members ring containing two carbon atoms and one oxygen atom

Are epoxides reactive?

Yes, very

Why are amines formally chiral but cannot be resolved?

Because the lone pair inverts to the other side of the molecule

How can amines be deprotonated?

By a sufficiently strong base (eg. Tert-butyl lithium)