Diene Allylic Chemistry Review General class name for

Diene & Allylic Chemistry Review General class name for each kind of diene listed below: Isolated diene cumulated diene conjugated diene Which structure above is actually wrong as drawn ? cumulated diene. . should look like…? Name me: 2, 4 -pentadien-1 -ol

Brief Diene Review (cont. ) ethanol + Na. OH An alkenyl halide Name of the reaction above ? Solvent? + H 2 O +Na. Cl Dehydrohalogenation 80% H 2 SO 4 An alkenyl alcohol + H 2 O Name of the reaction above ? Dehydration What other alkenyl alcohol could be used above ?

Brief Diene Review (cont. ) Reactions of dienes are always…. Additions Name three major diene addition reactions 1)Addition of HX 2)Addition of X 2 3)Addition of dienophiles go by at least 3 different names. What are they ? 1, 3 -cycloaddition 2+4 cycloaddition heat A reaction condition Who is the dienophile above ? Diels-Alder reaction

Brief Diene Review (cont. ) No reaction. Diene is not conjugated diene.

Brief Diene Review (cont. ) + If the foregoing reaction is occurring with HCl as the source of H+ a) Draw the most kinetically likely product b) Draw thermodynamically most likely product

Brief Diene Review (cont. ) Predict all 3 dibromide products of reacting the diene shown here in Br 2/dry CCl 4 Primaries Which one is kinetically favored? Secondary Which one is thermodynamically favored?

Vinyl site Allyl review Where is/are the allylic site(s) here ? What am called ? Allylic site Which site is the reactive site ? Allylic site Radical allylic chemistry favors/prefers…. . Symmetric radicals Carbocation allylic chemistry favors/prefers…. . Higher degree carbocations

Allyl Chemistry review (continued) Both the allylic carbocation and radical mechanism share what common electronic charge transfer behavior ? Both feature electron shift towards radical or carbocation site to produce alternative intermediates Carbocation allylic shift radical allylic shift What two factors govern formation of the most stable radicals above ? 1) Seeks symmetric resonance 2) Minimizes steric hindrance

Allyl Chemistry review (continued) Which is more likely to form , A or B ? A B What factor governs the choice of B as more likely above? Minimizing steric crowding (hindrance) What is the most likely product of: What factor governs the choice above? Radical intermediate forms symmetric resonance

The hydrolysis reaction shown is: • Radical based • Carbocation based • S N 1 • Eat dirt Doc A Quicky Allyl Chemistry review (continued) What is(are) the carbocation(s) in the above reaction ? A Primary B Secondary Which is kinetically favored and why? A, since + charge is on 3 o site Why is B thermodynamically favored ? More substituted around double bond (Zaitsev’s rule)

Allyl review (continued) yes Symmetric radical ? no Symmetric radical ? yes

Allyl review (continued) + primary Which of the two products above is thermodynamically favored ? Is a symmetric radical possible for this diene ? secondary Secondary No

Don’t snooze yet ! There’s more !! Exciting times with Aromaticity ahead !! Read Ch. 15