5: Alkenes Flashcards
(45 cards)
Alkenes
hydrocarbons with a carbon-carbon double bond.
Called unsaturated hydrocarbons cuz they have < the max # of H.
Dregree of unsaturation
the # of π bonds or rings in a molecule
Degree of unsaturation formula
2(n)+2-#H
2
n=#carbons
Alkane general molec formula
acyclic: CnH2n+2
cyclic: CnH2n
Alkene general molec formula
acyclic: CnH2n
cylcic: CnH2n-2
alkene naming
the suffix is “ene” replacing the -ane.
since the double bond is the functional group of an alkene.
Cyclopentene
Longest chain w/ functional group is given lowest #
Ex: CH3CH=CHCH2CH2CH3
2-hexene
stereoisomers def
isomers that differ in the way their attoms are arranged in space
stereo isomers named using
- cis:* meaning same (same plane)
- trans: *meaning different (diff plane)
compound with two double bonds
-diene
cyclic molecules
a double bond in a cyclic is always belween C 1 &2
trans-1,2-dichloroethene
Naming practice
(E)-3-chloro-4-methyl-2-pentene
vinylic carbons
the sp2 carbons of an alkene
allylic carbons
attached to an vinylic carbon, is also sp3
E/Z system
for alkenes that do not have a H attached to each of the sp2 carbons
IUPAC
Naming with E/Z
- break by DB & determine priotities of groups bonded to each of carbons. (priorities depend on atomic #)
- Z higher priotities on same side
- E higher priorities on opposite sides
“Z” isomer
“zee zame zide” higher priotities on same side
“E” isomer
high-priority groups on opposite sides
if atom is DB
treat as if it were single bonded to two atoms
if atom is triple bonded
treat as if 3 single atoms are there
priority with isotopes
the isotope with higher mass number has higher priority
electrophile
electron deficient atom
“electron loving”
spot: inc octet, positive charge, or partial positive, acid
