Organic 10: Conjugation in Alkadienes & Allylic Systems Flashcards
Allylic carbocation
a carbocation in which the positively charged carbon is allylic
Allylic free radical
a free radical in which the unpaired electron is on an allylic carbon
Allylic anion
a carbanion in which the negatively charged carbon is allylic
Conjugated diene
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
Conjugated systems
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
Allylic
sp3 hybridized carbon of a C=C-C unit
Vinylic
a carbon that is doubly bonded to another carbon
Allylic rearrangement
reactions of allylic systems that yield products in which double-bond migration has occurred
Alkadiene
a hydrocarbon that contains 2 double bonds
Isolated diene
units in which 2 carbon-carbon double bond units are separated from each other by one or more sp3-hybridized carbon atoms
Conjugated dienes
two carbon-carbon double bond units are connected to each other by a single bond
Cumulated dienes
one carbon atom is common to 2 carbon-carbon double bonds
Allene
the compound H2C=C=CH2 (1,2-propadiene)
Delocalization energy
increased stability due to conjugation; AKA resonance energy or conjugation energy
Elastomers
a synthetic polymer that possesses elasticity
Copolymer
polymer assembled from 2 or more different polymers
1, 2 Addition (Direct Addition)
addition of reagents of the type X-Y to conjugated dienes in which X & Y add to adjacent doubly bonded carbons
1, 4 Addition (Conjugate Addition)
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
Kinetic control
reaction in which the major product is the one that is formed at the fastest rate
Thermodynamic control
reaction in which the reaction conditions permit 2 or more products to equilibrate, giving predominance of the most stable product
Diels-Alder reaction
conjugate addition of an alkene to a diene
Dienophile
“diene seeker”; the alkene that adds to the diene
Cycloaddition
addition in which a ring is formed via a cyclic transition state
Pericyclic reactions
concerted reactions such as Diels-Alder cycloaddition that proceed through a cyclic transition state
Alder rule
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
