Properties Nomenclature Stability Addition Reactions Alkenes Properties Nomenclature Stability Addition Reactions

Ethylene

Electron Rich p-Bond

Elements or Degrees of Unsaturation: p-Bond or Ring

Determine the # elements of Unsaturation

Alkene Nomenclature

Cyclic alkenes

Alkyl Groups with p-Bonds

Alkylidene Groups Double Bonds Fused to Rings

Polyenes

Name these Alkenes

Cis and Trans no rotation about p-bond

cis-trans Isomers

E/Z System

Establish Priority of Substituents on Each sp2 Carbon

What’s My Name?

(Z)-4-ethyl-5-isopropyl-4-nonene

Priorities with Multiple Bonds

E or Z?

E or Z?

Name These

Hydrogenation Data Helps to Determine Stability DHhydrogenation of Alkenes

Enthalpy Change Shows Relative Energy of Alkene

Both cis and trans 2-Butene are Hydrogenated to Butane

“E” is More Stable than “Z” by 2.3 KJ/mol

Relative Stabilities of Alkenes

The Addition Reaction

HBr Addition

Markovnikov’s Rule The addition of H-X across a double bond results in the more highly substituted alkyl halide as the major product.

Depicting a Reaction

Addition of HBr or HCl Markovnikov Addition

Regiochemistry Determined by Stability of Intermediate

Hyperconjugation

Carbocation Stability more highly substituted, lower energy

3o Carbocation forms Preferentially

What Alkenes are Needed to form Theses Alkyl Halides?

Definitions Regioisomers – two constitutional isomers that could result from an addition reaction. Regiospecific – only one regiosisomer forms at the expense of the other. Regioselective – both regioisomers are formed, but one is formed in preference.

Determine the major product:

Rearrangements

Propose a Mechanism