Alkenes Flashcards
How to name alkenes?
Like alkanes but replace ending with ene instead of ane
What kind of isomers are cis and trans?
Stereoisomers because they’re arranged differently in space
How is a cis stereoisomer arranged?
groups on same side of double bond
How is a trans stereoisomer arranged?
Groups on opposite sides of double bond
What is more stable cis or trans isomer?
Trans since bigger groups are further apart so less repulsion
What is a stereoisomer?
Molecule differs due to the spatial arrangement of atoms. They have the same molecular formula
How to assign cis or trans?
Assign priority using molecular weights, two highest are used. See if they are same side of double bond (cis) or opposite sides (trans)
What are the letters used instead of cis and trans?
E (trans) Z(cis)
Zame zide
What is stronger a pi bond or sigma?
Sigma is stronger, pi is higher in energy also ‘exposed’
What orbitals make a pi bond?
2 p orbitals overlap above and below the sigma bond
Is rotation possible about pi bonds
No
Why is trans more stable than cis?
b/c the groups are further apart in trans so less repulsion
Whats more reactive, pi bond or sigma bond?
Pi, its shorter, has a higher electron density more exposed and less stable
Are alkenes miscible with water?
No they aren’t polar they’re hydrophobic
Do alkenes generally have higher or lower m/b points than equivalent alkanes?
Lower m/b points since it is harder to pack alkenes. Not as good packing means London dispersion forces can’t form as strongly
