Alkenes Flashcards
(38 cards)
What is a C=C double bond?
An area of high electron density
Why are alkenes highly reactive?
Their C=C double bond
How is the C=C double bond formed?
The overlap of a spare unbonded singly filled p-orbital present on each carbon atom in the bond
Can a C=C double bond be rotated?
NOPE
What is the general formula for alkenes?
Cn H2n
What is the bond angle and shape name for the C=C double bond in alkenes?
120
Planar
When naming alkenes what must you always check for?
E/Z isomerism
What is the only mechanism in the alkenes topic?
Electrophilic addition
Are alkenes or alkanes more reactive?
Alkenes
What is an electrophile?
A species that Accepts a pair of electrons
What area of alkenes is easily attacked by electrophiles?
Why?
The C=C double bond
It has a high electron density
Describe the mechanism to turn alkenes to alkanes briefly
Give this mechanism’s name
An electron pair is donated to the electrophile which causes C=C double bond to break, allowing each C to form bonds with other species
Electrophilic addition
Describe the electrophilic addition mechanism with the electrophile X-Y
1) an e- pair from the C=C bond forms a covalent bond with the delta positive X, breaking the X-Y bond and forming a :Y- ion. An intermediate with a *ve carbocation is formed
2) lone pair on :Y- forms a covalent bond with +ve carbon
In electrophilic addition with Bromine water, what does the :Br- ion act as?
A nucleophile
Bromine water is non-polar. How does electrophilic addition occur?
Electron rich double bond induces a dipole and delta positive Br acts as the electrophile
In a H-X molecule, where X is a halogen atom, which is delta positive?
The H is delta positive
How to write sulphuric acid for electrophilic addition
H-OSO3H
What is hydrolysis?
Splitting a molecule with water or another small molecule
What does the addition of ethyl hydrogen sulphate to water cause and produce?
What is the overall equation?
What does H2SO4 act as? Why?
Hydrolysis
Ethanol
CH2=CH2 +H2O —-> CH3CH2OH
A catalyst. It is not used up?
What is the most stable carbocation?
The least stable?
Tertiary
Primary
What is the major product formed from?
The more stable carbocation
How do you determine the class of the carbocation?
The number of carbon atoms directly bonded to the positively charged carbon atom
What is the stability of carbocations related to?
Why?
The presence of alkyl groups (CH3, CH2, CH)
Electron releasing relative to the hydrogen atoms and help to stabilise the positive charge on the carbocation
What is the electron releasing property of alkyl groups called?
Positive inductive effect
