Alkenes Flashcards
Why are alkenes unsaturated?
They contain a double bond
Why does carbon form 4 bonds?
Has 4 electrons in its outer shell
How does carbons bond in place alkenes?
3 electrons used in sigma bonds
1 used in pi bond
What is a pi bond?
The sideways overlap of two adjacent p orbitals above and below the plane of the bonding carbon atoms
Where is there a region of electro density in an alkenes?
Concentrated above and below the carbon bonding atom in the pi bond
Why do alkenes form stereoisomers?
Pi bonds locks carbons in position and prevents rotation around the c=c double bond
What is the C=C bond made up of?
Sigma bond and pi bond
What is the shape and bond angle around a C=C bond?
120 degrees
Trigonal planar
3 bonding regions repel as far as possible in one plane
What is a stereoisomerism?
Same structural formula but different arrangement of atoms in space
What are the requirements for E/Z isomerism?
A C=C double bond
Different groups attached to each carbon atom of the C=C bond
What is the difference between cis-trans and E/Z isomerism?
Cis trans require one of the groups in each carbon of the C=C double bond to be a Hydrogen atom
What phrase helps us remember which isomerism is Z?
Zame Zide
What are the rules for assigning priority in E/Z isomerisms?
- atom attached directly to the carbon in the C=C with the highest atomic number has the highest priority
- if the two highest priority are the same side it’s a z isomer
Is a Pi bond of Sigma bond weaker?
Pi bond
