Chemistry- organic 1

What does nomenclature mean?

The system used for naming organic compounds

Molecular formula

The actual formula

Empirical formula

Simplest whole number ratio of atoms in a molecule

Displayed formula

Shows every atom and every bond

Structural formula

Shows the arrangement of atoms without showing bonds

Homologous series

A series of organic compounds with the same functional group

Functional group

A group of atoms responsible for characteristics

General formula of Alkanes

CnH2n+2

General formula of alkenes

CnH2n

Saturated

Only single bonds

Unsaturated

At least one double carbon bond

Structural isomerism

Same molecular formula but different structural formula

What are the 3 ways in which structural isomers can be formed?

Alkyl group can be in different places

functional group position

different functional group

Stereoisomers

organic compounds with the same molecular formula but have different arrangements

What is E/Z isomerism and how are the decided?

caused by the limited rotation around a C=C bond

If the two substitutes with the highest Mr are on the same side then Z, if not the E

Cis-trans isomerism

A special type of E/Z isomerism where the two substituents on each carbon atom are the same

What is homolytic fission?

It happens when each bonding atom receives one electron from the bonded pair forming two radicals

What is heterolytic fission?

When one bonding atom receives both electrons from the bonding pair

What are radicals?

Highly reactive neutral species

How is a covalent bond formed from two radicals?

The radicals collide and the electrons are involved in the bond formation

What is an alkane?

A saturated hydrocarbon containing C-H bonds only

How are alkane fuels obtained

From the fractional distillation, cracking and reforming of crude oil

Describe the process of fractional distillation

1. Oil is preheated and passed through column

2. fractions condense at different heights

3. larger molecule= larger London forces

4. similar molecules condense at same height

5. small molecules condense at lower temperatures

What is cracking?

The process of converting large hydrocarbons to smaller molecules by breakage of C-C bonds

What is the reforming of crude oil

the process of straight chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion

What is the shape and angle of an alkane?

Tetrahedral 109.5

Describe the sigma bond in an alkane

a covalent bond which has a direct overlap of the electron clouds of the bonding atoms

How reactive are alkanes

Very unreactive

What reactions will alkanes undergo?

combustion and reaction with halogens?

What type of reaction is combustion?

oxidation

What is complete combustion?

combustion that occurs with plentiful supply of air

What are the products of complete combustion when alkanes are used?

carbon dioxide and water

What is incomplete combustion and what products are formed in the case of alknes?

Combustion in a limited supply of oxygen

water, CO2, CO

What pollutants are formed in the combustion of alkanes?

Carbon monoxide, oxides of nitrogen and sulfur, carbon particulates and unburned hydrocarbons

What is the environmental impact of soot?

Asthma, cancer and global warming

What are the environmental impacts of nitrogen oxides?

NO is toxic and can form smog

NO2 is toxic and acidic and forms acid rain

What are biofuels?

fuels developed from renewable resources. Alcohols and biodiesel are examples

How are halogenoalkanes formed from alkanes?

Radical substitution

In the presence of what does alkanes react with halogens

UV light

What are the three stages of free radical substitution?

Initiation, propagation and termination

What is initiation in free radical substitution?

breaking halogen bond to form free radicals

What is propagation in free radical substitution?

chain part of the reaction where products are formed but free radicals remain

What is termination in free radical substitution?

free radicals removed, stable products formed

Write the initiation equation for the reaction of CH4 with Cl to form CH3Cl

Cl2—> 2Cl*

Write the propagation equations for the reaction of CH4 with Cl to form CH3Cl

Cl*+CH4—> HCl + CH3*

*CH3 + Cl2 —> CH3Cl + Cl*

Write the termination equations for the reaction of CH4 with Cl to form CH3Cl

*CH3 + Cl* —> CH3Cl

2Cl* —> Cl2

CH3 + CH3 —> CH3CH3

What are the limitation of free radical substitution?

If there is excess halogen further substitution will take place therefore the desired product will be harder to separate from the others

What are alkenes?

Unsaturated hydrocarbons that contain at least one C=C bond made up of a pie bond and a sigma bond

How is a pie bond formed

Electrons in the adjacent p orbitals overlap above are below the carbon atoms

What bond restricts the rotation of carbon bonds?

pie bond

What is the angle and shape of a double bond?

Trigonal planar 120

What is the qualitative test for alkanes?

This test for C=C bond using bromine water. If the alkane is present, bromine water decolourises

Are alkenes or alkanes more reactive? And why?

More reactive due to high electron density of double bond and the fact the pi-bond is slightly easier to break

What intermolecular forces of attraction do alkenes have?

Only London forces due to non-polar bonds

What are the types of isomers that can be formed using alkenes?

E/Z isomers- due to the restricted rotation

Cis-trans isomers- if two of the same substituents are attached to each other

What is an electrophile?

species that are electron pair acceptors

What conditions are needed for the electrophilic addition of H20 to an alkene?

steam in the presence of an acid catalyst usually phosphoric acid

What are the products of the hydration reaction?

An alcohol

What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?

Hydrogen halide gases must be at room temperature

How does a molecule with a non-polar bond react as if it is an electrophile?

C=C bond with a high electron density induces a temporary dipole in the halogen molecule

What is the reaction called when a halogen is added to an alkene>

halogenation