Ch 16 - Conjugation, Resonance, & Dienes

Question 1

Trend of heat of hydrogenation & dienes?

Answer 1

• More stable diene ➡ smaller heat of hydrogenation

* stability: conjugated diene (1,3) > isolated diene (1,4)

Question 2

Hydrohalogenation (add of HX) in isolated diene ➡ product?

Answer 2

1,2 product only (markovnikov)

Question 3

Hydrohalogenation (add HX) of conjugated diene product?

Answer 3

• 1,2 (major at lower temp, kinetic, faster)

* 1,4 (major at higher temp, thermodynamic, more stable)

Question 6

Diels alder rules:

1) what confirmation must diene be in to react?

Answer 6

S-cis
• 1,3-cyclopentadiene ALWAYS rxts
• s-trans never rxts

Question 7

Diels alder rules:

2) what increases rxn rate?

Answer 7

EW subs on dienophile (e.g. C=O)

Question 8

Diels alder rules:

3) stereochemistry of DA rxn?

Answer 8

Stereochemistry of dienophile retained in product

Question 9

Diels alder rules:

4) when endo & exo products made, which is preferred?

Answer 9

Endo

Question 10

Diels Alder reagent? (diene + dienophile)

Answer 10

Heat

Question 11

Diels Alder product?

Answer 11

Forms 1 pi and 2 sigma bonds