Alkenes
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What are alkenes?
Alkenes are unsaturated hydrocarbons, containing at least one carbon - carbon double bond
Why are alkenes classified as unsaturated?
This is because they contain at least one carbon- carbon double bond
Why are alkenes more reactive than alkanes? (alk. - C=C - high elec. dens. - +react. - sng. C-C - alk.)
Alkenes have carbon - carbon double bonds which have a high electron density, making them more reactive than the single C-C bonds in alkanes
How are alkenes produced industrially? (alk. - prod. ind. - thrml. crck. - crd. oil.)
Alkenes are produced industrially through the thermal cracking of crude oil
What is the general formula for alkenes?
CₙH₂ₙ
Why can’t atoms rotate around the C=C double bond in alkenes?
Alkene have a pi - bond which restrict the structure and prevent the rotation of atoms around the carbon double bond. Hence, locking the atoms in place
If a hydrogen atom in ethene is swapped for another atom or group, what happens to the shape of the molecule?
The molecule remains flat around the carbon - carbon double bond because the planar shape is determined by the double bond
What three types of isomers can alkenes with more than three carbon atoms form?
• Chain isomers • Position isomers • Geometrical (E/Z) isomers
What are position isomer in alkenes?
Isomers where the double bond is in different positions within the carbon chain
How does carbon chain length affect the number of possible isomers?
A longer carbon chain gives more possible arrangements, so more isomers
What is geometrical isomerism?
A type of stereoisomerism where molecules have the same structural formula but different spatial arrangement around a C=C double bond
In E/Z isomerism, what does the Z - isomer indicate?
Z = priority groups are on the same side of the C=C bond
In E/Z isomerism, what does the E isomer indictae?
E = priority groups are on opposite sides of the C=C bond
How does the double bond in alkenes affect physical properties like melting and boiling points?
It has little effect, alkenes have similar physical properties (melting and boiling) to alkanes
What type of intermolecular forces act between alkene molecules?
van der Waals are the only intermolecular forces between alkene molecules
How do melting and boiling points change with increasing carbon chain length in alkenes?
They increase as the number of carbon atoms increases
What is an electrophile?
An electron deficient species that accepts an electron pair