Organic 10: Conjugation in Alkadienes & Allylic Systems

Question 1

Allylic carbocation

Answer 1

a carbocation in which the positively charged carbon is allylic

Question 2

Allylic free radical

Answer 2

a free radical in which the unpaired electron is on an allylic carbon

Question 3

Allylic anion

Answer 3

a carbanion in which the negatively charged carbon is allylic

Question 4

Conjugated diene

Answer 4

system of the type C=C-C=C, in which 2 pairs of doubly bonded carbons are joined by a single bond; the pi electrons are delocalized over the unit of 4 consecutive sp2 hybridized carbons

Question 5

Conjugated systems

Answer 5

a structural arrangement in which electron delocalization permits 2 groups to interact so that the properties of the conjugated system are different from those of the separate groups

Question 6

Allylic

Answer 6

sp3 hybridized carbon of a C=C-C unit

Question 7

Vinylic

Answer 7

a carbon that is doubly bonded to another carbon

Question 8

Allylic rearrangement

Answer 8

reactions of allylic systems that yield products in which double-bond migration has occurred

Question 9

Alkadiene

Answer 9

a hydrocarbon that contains 2 double bonds

Question 10

Isolated diene

Answer 10

units in which 2 carbon-carbon double bond units are separated from each other by one or more sp3-hybridized carbon atoms

Question 11

Conjugated dienes

Answer 11

two carbon-carbon double bond units are connected to each other by a single bond

Question 12

Cumulated dienes

Answer 12

one carbon atom is common to 2 carbon-carbon double bonds

Question 13

Allene

Answer 13

the compound H2C=C=CH2 (1,2-propadiene)

Question 14

Delocalization energy

Answer 14

increased stability due to conjugation; AKA resonance energy or conjugation energy

Question 15

Elastomers

Answer 15

a synthetic polymer that possesses elasticity

Question 16

Copolymer

Answer 16

polymer assembled from 2 or more different polymers

Question 17

1, 2 Addition (Direct Addition)

Answer 17

addition of reagents of the type X-Y to conjugated dienes in which X & Y add to adjacent doubly bonded carbons

Question 18

1, 4 Addition (Conjugate Addition)

Answer 18

addition reaction in which the reagent adds to the termini of the conjugated system with migration of the double bond; synonymous with 1, 4 addition; the most common examples include this type of addition to 1, 3-dienes & to alpha, Beta-unsaturated carbonyl compounds

Question 19

Kinetic control

Answer 19

reaction in which the major product is the one that is formed at the fastest rate

Question 20

Thermodynamic control

Answer 20

reaction in which the reaction conditions permit 2 or more products to equilibrate, giving predominance of the most stable product

Question 21

Diels-Alder reaction

Answer 21

conjugate addition of an alkene to a diene

Question 22

Dienophile

Answer 22

“diene seeker”; the alkene that adds to the diene

Question 23

Cycloaddition

Answer 23

addition in which a ring is formed via a cyclic transition state

Question 24

Pericyclic reactions

Answer 24

concerted reactions such as Diels-Alder cycloaddition that proceed through a cyclic transition state

Question 25

Alder rule

Answer 25

rule of maximum accumulation of unsaturation: in a Diels-Alder raction, the major stereoisomer is derived from the transition state in which unsaturated groups in the dienophile are endo with respect to the diene