Alkenes Flashcards
What does the double bond in alkenes mean to reactivity?
Makes them more reactive than alkanes
The double bond forms an electron-rich area in the molecule which can be easily attached by an electrophile (electron liking - electron pair acceptors)
General formula of alkenes
CnH2n
What is the shape of ethene?
Planar
Angles between each bond roughly 120 degrees
Is there rotation about the double bond in alkenes?
No
Why can’t a double bond rotate?
The two p-orbitals overlap to form a cloud of electron density about the below the double bond (pi orbital)
Sometimes called restricted rotation
What are the two types of isomers that alkenes can form (that involve double bonds)?
- Position isomers
- Geometrical isomers
What are the only intermolecular forces acting between alkene molecules?
van der Waals
The physical properties of alkenes are similar to those of…
Alkanes
The melting and boiling points increase with…
the number of carbon atoms present
Are alkenes soluble in water?
No
Do alkenes burn in air?
Yes
What are the typical alkene reactions?
Electrophilic addition reactions
General mechanism for electrophilic addition
- Electrophile attracted to double bond
- Electrophile + and accept pair of electrons from double bond
- Positive ion (carbocation) formed
- Negative charged ion forms a bond with carbocation
Are electrophiles positive or negative?
Positive
Definition of electrophile
Electron pair acceptor
Attracted to areas with a lot of electrons/high negative charge
