Alkenes Flashcards
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 double bond
What feature makes alkenes more reative than alkanes?
The carbon - carbon double bond has a high electron density, making alkenes more reactive
What are some common products made from ethene?
Polymers like PVC, polyethene and polystyrene
How are alkenes produced industrially?
Alkenes are produced in large quantities by the thermal cracking of crude oil
What is the general formula for alkenes with one carbon - carbon double bond?
CnH2n
What is the shape of the ethene molecule?
Ethene is a planar (flat) molecule with bond angles of about 120 degrees
Why can’t atoms rotate around the C=C double bond in alkenes?
The structure of the double bond restricts rotation due to the presence of a pi - bond, which locks the atoms in place
If a hydrogen atom in ethene is swapped for another atom ro 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 types of isomers can alkenes with more than three carbon atoms?
Alkenes can form chain isomers, position isomers and geometrical (E/Z) isomers
What is a position isomer in alkenes?
An isomer where the double bond is located in a different poitin along the carbon chain
What increases the number of possible position isomers in alkenes?
A longer carbon chain, which allows the double bond to occur in more positions
What condition must be met for E/Z isomerism to occur in alkenes?
Each carbon in the double bond must be bonded to different groups
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
