Test 4

Question 1

One Way to Prepare Alkyl Halides

Answer 1

Free Radical Halogenation

Question 2

Problems with Free Radical Halogen.

Answer 2

i. Random placement of halogen
ii.Creates products with potentially more than one halogen on the compound.

Question 3

Better Ways to male am Alkyl Halide

Answer 3

1)Change an alcohol into an alkyl halide using a strong binary acid such as HCl or HBr.

This technique works BEST if the halogen is attached to a tertiary carbon.

Question 4

Tertiary Carbon Alkyl Halide

Answer 4

Change an alcohol into an alkyl halide using a strong binary acid such as HCl or HBr.

This technique works BEST if the halogen is attached to a tertiary carbon.

Question 5

Secondary and Primary Carbon Alkyl Halides

Answer 5

If you have a primary or secondary alcohol you must use a special catalyst: (page 222)
Chlorination: SoCl2
Bromination: PBr3

Question 6

How can we remove a Halogen from an Alkyl Halide

Answer 6

Grignard Reagent: (Mg)

Question 8

SN2 Reaction Conditions

Answer 8

How many steps: 1

Where is attack by nucleophile: backside attack

The nucleophile (lewis base) replaces a weaker Lewis base.

What about the products and stereochemistry: stereochemical inversion R–> S Levo to Dextro

The best substrate: Primary or possibly secondary substrate

Two types won’t work at all for substrate: Aryl (benzene), Vinyl (attached to C=C)

Rate dependence: Both substrate and nucleophile (2 in Sn2) means bimolecular

Question 8

SN1 Reaction Conditions

Answer 8

How many steps: 2

First a carbocation intermediate is formed SLOW (Rate limiting step)

The carbocation is attacked by the nucleophile FAST

Rate dependence: only depends upon concentration of substrate and not nucleophile.

Stereochemistry: Since the carbocation is Flat and sp2 hybridized the nucleophile has a 50/50 chance of attack from the top or the bottom of the carbocation. This leads to a RACEMIC mixture which is non-optically active.

One base is replacing another base, but there is NO relationship in base strength because this occurs in two steps.

Since we must form a carbocation we must have some mechanism so that the carbocation can be formed.

Best substrate: tertiary substrate since a more stable carbocation is formed (maybe secondary)

Question 8

Nucleohphile

Answer 8

Lewis Base

Question 8

SN2 What would happen

Answer 8

What would happen the rate of a Sn2 reaction if we:

Double the concentration of nucleophile: rate increases 2x

Double the concentration of substrate: rate increases 2x

Double BOTH the concentration of nucleophile and substrate: rate will increase 4x

Question 8

SN 1 What would happen

Answer 8

We doubled the concentration of substrate 2x

We doubled the concentration of nucleophile rate will not change

We doubled the concentration of substrate and nucleophile 2 x

Question 8

E2 Reaction

Answer 8

E2 mechanism:

Single step

The H and halogen which will leave must be anti-periplanar (opposite sides of the molecule)

This mechanism works best if a STRONG base is used

Question 8

E1 Mechanism

Answer 8

Two steps

Carbocation intermediate

Works best with a tertiary substrate (not primary)

Question 8

Alcohols: Some common alcohols

Answer 8

CH3OH : Methanol: Wood Alcohol
CH3CH2OH: Ethanol: Grain Alcohol
Isopropyl Alcohol : Rubbing Alcohol
1,2,3- propanetriol: Glycerol

Question 9

Oxidation Reduction Organic Chemistry

Answer 9

Oxidation: gain of oxygen or loss of hydrogen

Reduction: gain of hydrogen or loss of oxygen

Question 9

Oxidation Reduction Series of Alcohols

Answer 9

Primary Alcohol to Aldehyde to Carboxylic Acid
Secondary Alcohol to Ketone to No reaction (except Alphahydroxketone)
Tertiary Alchol to No Reaction

Question 9

common oxidizing agents

Answer 9

KMnO4 KCr2O7 KCrO4 O2

Question 9

common reducing agents

Answer 9

NaBH4 NH3 H2

Question 10

Mild and Strong Reducing Agents

Answer 10

Mild: NaBH4
Strong LiAlH4

Question 11

Mild and Strong Oxidizing Agents

Answer 11

Mild: PCC
Strong: KMNO4

Question 12

How to Produce Phenol

Answer 12

1. Benzene Sulfonation
2. Treatment with Strong Base

Question 13

Ether Acid Cleavage

Answer 13

ACIDIC CLEAVAGE of ETHERS to form an Alcohol and an Alkyl halide using a strong binary acid (HCl, HBr or HI)

The cleavage of an ether can take place EITHER by an Sn1 mechanism or an Sn2 mechanism so the products formed depend upon the type of ether that we start with.

Primary or secondary ethers occur by an Sn2 pathway: Halogen will attach to the compound that is a lower order
f there is a tertiary carbon involved in the cleavage, then the tertiary carbon will get the halogen and the other carbon will become the alcohol.

Question 14

Oxidation of Sulfides

Answer 14

sulfides are oxidized to disulfides

Question 15

Leaving Groups

Answer 15

In an Sn2 reaction the best leaving group is a WEAK base

Question 16

Williamson Ether Synthesis

Answer 16

Alcohol + Alkyl halide ---> Ether This is an Sn2 mechanism. Change the alcohol into an alkoxide In forming the ether you want the alkoxide to be the MORE hindered substrate and the alkyl halide to be the less hindered substrate.