UNIT 9 - Alkyl Halides

R-O-R

Ether

ROH, -OH

Alcohol

R-X

Alkyl

What is Alkyl Halides?

It contains one carbon-halogon bond

Alkyl Halide

Give examples of properties and uses of Alkyl Halide

• Fire-resistant solvents

• Refrigerant

• Pharmaceutical and precursors

has one R group attached to carbon linked to the halogen

Primary (1°) halogenoalkanes

has two R group attached to carbon linked to the halogen

Secondary (2°) halogenoalkanes

has three R group attached to carbon linked to the halogen

Tertiary (3°) Halogenoalkanes

Are Halide ions (Br, Cl, I) soluble or insoluble in water?

Halides are INSOLUBLE in water

what happens to the Boiling point if the Molecular weight increase

Boiling point increase

Arrange in order the Boiling point of Halogen (F, Cl, Br, I)

1. Iodine

2. Bromine

3. Chlorine

4. Fluorine

What is the mechanism of Sn1 and Sn2

• Sn1 - two step mechanism

• Sn2 - one step mechanism

Explain the mechanism of SN1

SN1 (two mechanism)

• Mechanism:

  • Step 1: Slow, rate-determining step — the alkyl halide dissociates to form a carbocation and a leaving group.

  • Step 2: Fast step — carbocation reacts with water as a nucleophile — alcohol is the product

  • Step 3: Proton is loss from the protonated intermediate — forming the neutral alcohol product.

What is the product of SN1 mechanism

Alcohol

Explain SN1 (Substrate, leaving group, nucleophile, solvent)

SN1 (two mechanism)

• Substrate:

  • SN1 reactions are best for tertiary, allylic, benzylic halides

• Leaving group

  • increase reaction = low energy

• Necleophile

  • Nucleophile must be nonbasic to prevent elimination of HX

• Solvent

  • Polar Solvents stabilize the carbocation

Explain SN2 (Substrate, leaving group, nucleophile, solvent)

SN2 (one-step mechanism)

• Substrate

  • SN2 is best for methyl and primary substrates.

  • Secondary reacts slowly

  • Tertiary does NOT react

• Leading group

  • Good leaving group (more stable anions)

• Solvent

  • Protic solvents lowers ground-state energy

• Nucleophile

  • Basic

it is:

• unimolecular reaction

• first order kinetic

• 2 steps mechanism

• rate of reaction: substrate only

• forms carbonation

• partially racemized

• mild nucleophile

• high polarity

SN1

It is a unimolecular reaction

SN1

it is:

• bimolecular reaction

• second order kinetics

• rate of reaction: BOTH — Substrate & Nuleophile

• only inverted

• strong nuclophile

• low polarity

SN2

the more highly substituted alkene products predominate

Zaitsev’s Rule

C—X breaks first = removal of proton (what kind reaction)

E1 reaction

what kind of reaction is: C—H & C—X breaks = Alkene in a single step without intermediates

E2 reaction

what kind of reaction: C—H breaks = loses -X = forms Alkene (double bond)

E1cB reaction

Alkyl Halide reaction is also known as…

Tosylate

Which substate does SN2 favors?

Primary and Secondary Substrate

Which substate does SN1 favors?

Tertiary Substrate

What are the 3 mechanisms of Elimination of Alkyl Halides

1. E1 reaction

2. E2 reaction

3. E1cB reactions

short term use form insomnia

Sedation - Chloral Hydrate

anaesthetic agent

Halothane

Give examples of Anaesthetic Agents

1. Halothane

2. Flurane

3. Nitrous Oxide

used as an insecticides

Diclorodiphenyltrichloroethane (DDT)

used as antibiotic

Chloromycetin (Chloramphenicol)

What are the Thyroid Hormones?

T3 and T4

A thyroid hormone:

• Thyroxine

• 4 iodine atoms

• Inactive forms

• 80% of Thyroid hormone production

T4

a thyroid hormone:

• Triiodothyronine

• 3 iodine atoms

• Active form

• 20% Thyroid hormone production

T3