Unformatted text preview: Bromination is highly regioselective for substitution of tertiary hydrogens. Major
F\ synthetic application is in synthesis of tertiary alkyl bromides. Chapter 5. Structure and Preparation of Alkenes: Elimination Reactions
- Structure and Bonding in Alkenes ~ Be able to name mono— and polysubstituted alkenes and cycloalkenes using systematic (IUPAC) nomenclature. Be
able to draw the structure corresponding to a given systematic name. - Use the Cahn—Ingold—Prelog sequence rules to differentiate between E- and Z- oleﬁns.
- Differentiate between cis- and trans-disubstituted alkenes. Remember/f." Cis and trans stereochemical notation is useful when substituents are identical or analogous (oleic acid has a cis double bond). Cis and trans notation is ambiguous when analogies are not obvious. — Alkenyl Groups HES = H2Q=QH= H23 =C3HCH2_ H22 =QCH3 neonate vinyl and _ I
— Isomerism in Alkenes.
- Physical Properties of Alkenes. Relative Stabilities of Alkenes
— Cycloalkenes; Stabilities of cycloalkene: cis trans isomers
rx trans—cyclooctene is smallest trans—cycloalkene that is stable at room temperature cis stereoisomer is more stable than trans through CH cycloalkenes
cis and trans—cyclododecene are approximately equal in stability.
When there are more than 12 carbons in the ring, trans-cycloalkenes are more stable than cis‘ The ring is large enough so the cycloalkene behaves much like a noncyclic one. For all reactions discussed, you should : - Know the reagents for and predict the products of the reactions
- ldenti the c of the mechanism - Write the mechanism where indicated (see below for KNOW TO WRITE THE MECHANISM); for all
others mechanism not reguired. Preparation of Alkenes:Elimination Reactions
ﬂ-Elimz'nation Reactions Overview:
1) dehydrogenation of alkanes:
2) dehydration of alcohols:
Regioselectivity in Alcohol Dehydration: The Zaitsev Rule
When elimination can occur in more than one direction, the principal alkene is the one formed by loss of H ﬁom the B carbon having the fewest hydrogens. ...
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- Summer '08
- Organic chemistry