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AP Chem Test 4 > Test 4 > Flashcards

Test 4 Flashcards

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1
Q

One Way to Prepare Alkyl Halides

A

Free Radical Halogenation

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2
Q

Problems with Free Radical Halogen.

A

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

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3
Q

Better Ways to male am Alkyl Halide

A

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.

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4
Q

Tertiary Carbon Alkyl Halide

A

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.

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5
Q

Secondary and Primary Carbon Alkyl Halides

A

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

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6
Q

How can we remove a Halogen from an Alkyl Halide

A

Grignard Reagent: (Mg)

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7
Q
A
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7
Q
A
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8
Q

SN2 Reaction Conditions

A

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

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8
Q

SN1 Reaction Conditions

A

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)

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8
Q

Nucleohphile

A

Lewis Base

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8
Q

SN2 What would happen

A

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

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8
Q

SN 1 What would happen

A

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

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8
Q

E2 Reaction

A

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

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8
Q

E1 Mechanism

A

Two steps

Carbocation intermediate

Works best with a tertiary substrate (not primary)

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8
Q

Alcohols: Some common alcohols

A

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

9
Q

Oxidation Reduction Organic Chemistry

A

Oxidation: gain of oxygen or loss of hydrogen

Reduction: gain of hydrogen or loss of oxygen

9
Q

Oxidation Reduction Series of Alcohols

A

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

9
Q

common oxidizing agents

A

KMnO4 KCr2O7 KCrO4 O2

9
Q

common reducing agents

A

NaBH4 NH3 H2

10
Q

Mild and Strong Reducing Agents

A

Mild: NaBH4
Strong LiAlH4

11
Q

Mild and Strong Oxidizing Agents

A

Mild: PCC
Strong: KMNO4

12
Q

How to Produce Phenol

A
  1. Benzene Sulfonation
  2. Treatment with Strong Base
13
Q

Ether Acid Cleavage

A

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.

14
Q

Oxidation of Sulfides

A

sulfides are oxidized to disulfides

15
Q

Leaving Groups

A

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

16
Q

Williamson Ether Synthesis

A

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.

AP Chem Test 4 (2 decks)

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