Organic Chem 3120

Calculating degrees of un-saturation
Compare fully saturated molecule to current with the following formula
#H+(1)#Halogens-(1)#N or S and (0) for Oxy
Cis / Trans isomerism

  • all terminal alkenes i.e. those with a C=CH2 unit do not exist as cis- and trans- isomers.
  • all 1,1-symmetrically disubstituted alkenes i.e. those with a C=CR2 unit do not exist as cis- and trans- isomers.
  • alkenes with the R-CH=CH-R unit can exist as cis- and trans- isomers.


Can Exist if R1 is not = to R2


R3 is not = to R4

Trans Isomer
Cahn-Ingold-Prelog priority rules

Rule 1) Rank the first atom according to atomic # w/ prioity based on higher number.

Rule 2) Continue to move away from the first until a difference is found.

Rule 3) Multiple bonds are counted as two or three bonds to single atoms

Zusammen Isomerism


The prioroity groups are on the same side.

Entgegen Isomerism


Priority groups on opposite sides
Markovnikov’s Rule
H will attach to the carbon with the fewest alkyl substituents and the X attaches to the carbon with the most alkyl sudstituents
Carbocation Stability-Rank Highest to lowest!
1) Tertiary
2) Secondary
3) Primary
4) Methyl
Hammond Postulate
The intermediate most closely resembles either the reactants or products depending which is ever is highest energy
Zaitsev’s Rule
The preferred product is the more highly substituted product therefore the more stable
Hoffman product
anti-Zaitsev’s Rule is the dominate or major product
Two most common elimination reactions to make a Alkene?
1) dehydrohalogenation
2) dehydration
Dehydrohalogenation of a Alkyl
Removal of a halogen and hydrogen with a strong base from a alkyl halide.

KOH + CH3CH2OH (ethanol)

Dehydration of a Alkyl
Removal of a water molecule of an alkyl alcohol with a strong acid.


Halogenation of a Alkene
Yeilds 1,2-dihalides

Only Br or Cl used

Halogenation yields Cis or Trans?
Yields only Trans
Halohydrin reactions
Add HO-Cl or HO-Br to the Alkene

reacts like halogenation and forms trans only

NBS and (DMSO) and H2O

The addition of H2O to a alkene (hydration)

Hg(OAc)2 + H2O + NaBH4

Adding H2O to a alkene
Oxymercuration follows Markovnikov’s Rule or not?
Follows Markonikov’s Rule
The addition of H2O with BH3 in a THF solvent.
Hydroboration follows Markovnikov’s Rule or not?
non-Markovnikov addition because of steric crowding.
Adds H to alkenes with the use of metals like Pd or Pt
Forming C-H or breaking C-O, C-N, C-X
The loss of electron density by carbon

Forming C-O, C-N, C-X or breaking C-H

The adding of three membered ring containing Oxygen

Treatment with a Acid creates a 1,2-diol

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