Halogenoalkanes

What is a haloalkane

An alkane where at least one hydrogen has been replaced with a halogen

What is primary halogenoalkane

If carbon boned to halogen is bonded to 1 carbon

What is secondary halogenoalkane

If carbon boned to halogen is bonded to 2 carbon

What is tertiary halogen

If carbon boned to halogen is bonded to 3 carbon

Whta is general formula for halogenoalkane

CnH2n+1X. X=halogen

What IMF forces do halgoalkanes

Experience permant dipole-dipole forces and Van der Waals so polar molecules

What happens to MP and BP as length of carbo chain increases

Van der Waals strength increases so MP and BP increases

Solubility of halogenoalkanes

halogenoalkane are polar so slightly soluble in water - hydrogen bond between water molecules tend to be stronger than permeant dipole-dipole forces

What happens to solubility as length of carbocation increases

Solubility decreases

What reaction mechanism for halogenoalkane

nucleophile substation

What conditions for reaction of halogenoalkanes → alcohols

-NaOH/KOH

Heat

What conditions for reaction of Halogenoalkane → nitrile

NaCN / KCN dissolved in ethanol

And heat

What conditions for Halogenoalkanes → 1 degree Amine

Heat under pressure

Excess ammonia

Why must have excess ammonia for Halogenoalkanes → 1 degree Amine

Excess to prevent further reaction of amine product

Reaction mechanism for Halogenoalkanes → Alcahol

Reaction mechanism for Halogenoalkanes → Nitrile

Reaction mechanism for Halogenoalkanes → 1 degree amine

Rate of reaction for halogenalkanes

The lower the bond enthalpy → less energy for activation energy → more collisions will be successful→ increase rate of reaction

List of hughest enthalpy to lowest enthalpy

C -F → highest enthalpy - slowest reaction

C - Cl

C - Br

C - I → lowest enthalpy - fastest reaction

How to measure reactivity

1. Dissolve compound in ethanol

2. Add AgNO3 and water

3. Measure time taken for silver nitrate and halogen precipitate to form

Elemimatiom reaction of halogeno alkanes

Halogenoalkane → alkene

Conditions for halogenoalkene → alkenes

NaOH/akOH dissolved in ethanol

Reaction is heated

Reaction mechanism for elimination reaction for elimination reaction of halogenoalkenes

What is hetrofission and what does it form

If a covalent bond breaks and both bonding electrons go to one atom

2 ions formed

Shat is homolytic fission and what does if form

If a covalent bond break and a electron goes to each atom

Product:2 free radicals

What is a free radical

Any species that contains unpaired electrons

X•

What is easiest way to form free radicals

UV light or high temp

What makes the it more likely a bind to go homolytic fission

The lower the bond enthalpy

Property of free radicals

Incredibly reactive

What forms when 2 free radicals

A molecule

A• + B• → A-B

What forms when a free radical and a molecule collide

A free radical and a new molecule

A• + B-B → A

Alkanes react with halogens in prescene of of UV loght to form

Halogenoalkane

What are 3 steps of free radical susbistition

Initiation

Propagation

Termination

What happens in initiation for CH4 + Cl2 → CH3Cl + HCl

X2 → 2X•

What happens during propagation for CH4 + Cl2 → CH3Cl + HCl

Cl• + CH4 →HCl + CH3•

CH3• + Cl2 → CH3Cl + Cl•

Termination step for CH4 + Cl2 → CH3Cl + HCl

Any of the free radicals react together

Cl• + Cl• → Cl2

Cl• + CH3• → CH3Cl

CH3• + CH3• → CH3CH3

Disadvantage of free radicals substitution

Very hard to control ( free radical too reactive)

In reality multiple products are formed

What is a chlorofluorocarbons

Compound that contains chlorine fluorine and carbon

What were chlorofluorocarbons used for

Refrigerators , solvents

Initiation for O zone deple

C2F4Cl2 → C2F4Cl• + Cl•

Propagation for ozone depleted

Cl• + O3 → ClO• +O2

ClO• + O3 → 2O3 + Cl•

Termination for Ozone depletion

2 free radical reacting

What is alternative of hydro fluorocarbons

Hydrocarbons

Why are hydrocarbons better

Contain stronger bond → less likely to break under UV light

Cannot produce Cl•