PHA615 LEC: Alkanes and Cycloalkanes

POLAR MECHANISM

• results from a heterolytic bond cleavage/formation.

POLAR MECHANISM

This is a more common reaction mechanism

Nucleophile (Nü)

neutral/negatively charged atom (e.g. HO-, H2O).

Electrophile (e+)

neutral/positively charged atom (e.g. C=O, R-X)

RADICAL MECHANISM

results from a homolytic bond cleavage/formation

RADICAL MECHANISM

a common reaction mechanism for alkanes/cycloalkanes in which a radical (an atom with a single unpaired electron) is formed at high temperature (Δ ) or irradiation (hv).

Activation Energy (Ea)

energy required to reach the transition state.

Transition state (Ts)

a state of peak free energy and where reactants starts to form products.

Delta G naught prime (Δ G°)

a free energy change of a reaction in standard condition.

Fast/Slow

refers to the amount of Ea to reach Ts; inversely proportional with Ea.

Exergonic reaction

• reactions that releases energy; has a negative G°.

Endergonic reaction

reactions that absorbs energy; has a positive G°.

Alkanes

General formula: CnH2n+2

Alkanes

referred to as saturated hydrocarbons (HC)

made up of completely single bonds.

Petroleum and natural gas

 are sources of alkanes and a mixture of hydrocarbons.

CYCLOALKANES

General formula: CnH2n

CYCLOALKANES

 they are also saturated hydrocarbons (HC) but has 2 fewer hydrogens compared to normal alkanes.

CYCLOALKANES

have their terminal carbons connected to created an enclosed cyclic system.

CYCLOALKANES

can be substituted with different atoms or functional groups similar to a normal alkane.

insoluble

• are _ in water.

  • Both of them exhibits London dispersion forces which is a non-polar IMF and is not soluble in polar molecule such as water.

lower densities

• have _than that of water.

  • They will not dissolve in water and furthermore they will even float.

length or size

• The boiling points increases as carbon chain increases in _.

  • As the carbon chain increases, the number of IMF also increases which is required to be broken for a material to boil.

least

_ reactive of all organic compounds but are not completely unreactive,

Combustion

• reaction between a substance and O2 that produces CO2 and H2O resulting in the production of large amount of heat and light.

Halogenation

chemical reaction between a substance and a halogen in which one or more halogen atoms are incorporated into molecules of the substance.

Primary carbon

3 hydrogens

1 carbon/r attached

Secondary Carbon

2 hydrogens

2 carbon/r attached

Tertiary Carbon

1 hydrogens

3 carbon/r attached

Quaternary carbon

0 hydrogens

4 carbon/r attached

Substitution

is a chemical reaction in which part of a small reacting molecule replaces an atom or a group of atoms on a hydrocarbon or hydrocarbon derivative.

Halogenation

is a chemical reaction between a substance and a halogen in which one or more halogen atoms are incorporated into molecules of the substance.

REACTIVITY-SELECTIVITY PRINCIPLE

states that the greater the reactivity of the species, the less selective it will be.

REACTIVITY-SELECTIVITY PRINCIPLE

• It aids in determining the most common halogenation product that can be formed.

Secondary Carbon

which alkyl chloride products is most likely to be formed

Tertiary Carbon

which alkyl bromide products is most likely to be formed