Test 1

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 two pairs of doubly bonded carbons are joined by a single bond. The pi electrons are delocalized over the unit of four consecutive sp2-hybridized carbons

Question 5

conjugated systems

Answer 5

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

Question 6

allylic carbon

Answer 6

The sp3-hybridized carbon of a C=C-C unit. Atoms or groups attached to an allylic carbon are termed allylic substituents.

Question 7

Hückel’s rule

Answer 7

Completely conjugated planar monocyclic hydrocarbons possess special stability when the number of their pi electrons = 4n + 2, where n is an integer.

Question 8

lowest unoccupied molecular orbital (LUMO)

Answer 8

The orbital of lowest energy that contains none of a molecule’s electrons; the lowest unoccupied molecular orbital.

Question 9

highest occupied molecular orbital (HOMO)

Answer 9

Highest occupied molecular orbital (the orbital of highest energy that contains at least one of a molecule’s electrons).

Question 10

isolated dienes

Answer 10

Diene of the type C=C-(C)x-C=C in which the two dbl bonds are separated by one or more sp3-hybridized carbons. Isolated dienes are slightly less stable than isomeric conjugated dienes.

Question 11

cumulated dienes/ cumulenes/ allenes

Answer 11

Diene of the type C=C=C, in which one carbon has dbl bonds to two others.

Question 12

resonance energy/delocalization energy/conjugation energy

Answer 12

Extent to which a substance is stabilized by electron delocalization. It is the difference in energy between the substance and a hypothetical model in which the electrons are localized.

Question 13

elastomers

Answer 13

A synthetic polymer that possesses elasticity

Question 14

copolymer

Answer 14

Polymer formed from 2 or more different monomers

Question 15

1,2 addition

Answer 15

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

Question 16

1,4 addition

Answer 16

Addition of reagents of the type X-Y to conjugated dienes in which X and Y add to the termini of the diene system

Question 17

kinetic control

Answer 17

Term describing a reaction in which the major product is the one formed at the fastest rate.

Question 18

thermodynamically controlled reaction

Answer 18

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

Question 19

Diels-Alder reaction

Answer 19

Conjugate addition of an alkene to a conjugated diene to give a cyclohexene derivative. Diels-Alder reactions are extremely useful in synthesis.

Question 20

dienophile

Answer 20

The alkene that adds to the diene in a Diels-Alder reaction.

Question 21

cycloaddition

Answer 21

Addition, such as the Diels-Alder reaction, in which a ring is formed via a cyclic transition state.

Question 22

pericyclic reactions

Answer 22

A reaction that proceeds through a cyclic transition state.

Question 23

endo/Alder rule

Answer 23

The preferred product in a Diels/Alder reaction where the interaction between the developing pi bond and the carbonyl groups present stablizes the dienophile as it is approaching. This results in the “outside” groups on the diene on the SAME side of the 6-membered ring as the electron withdrawing group (EWG).

Question 24

frontier orbitals

Answer 24

Orbitals involved in a chemical reaction, usually the highest occupied molecular orbital of one reactant and the lowest unoccupied molecular orbital of the other.

Question 25

symmetry-allowed reaction

Answer 25

Concerted reaction in which the orbitals involved overlap the phase at all stages of the process

Question 26

symmetry-forbidden

Answer 26

Concerted reaction in which the orbitals involved do not overlap in phase at all stages of the process

Question 27

Cope rearrangement

Answer 27

The thermal conversion of the 1,5-diene unit to another by way of a cyclic transition state.

Question 28

arene

Answer 28

Aromatic hydrocarbon. Often abbreviated ArH.

Question 29

aromaticity

Answer 29

Special stability associated with aromatic compounds.

Question 30

aliphatic hydrocarbon

Answer 30

Term applied to compounds that do not contain benzene or benzene-like rings as a structural unit. (Historically, aliphatic was used to describe compounds derived from fats and oils.)

Question 31

Kekulé structure

Answer 31

Structural formula for an aromatic compound that satisfies the customary rules of bonding and is usually characterized by a pattern of alternating single and double bonds. There are two Kekulé formations for benzenes: dbl bonds between C1=C2, C3=C4, C5=C6 or C2=C3, C4=C5, C6=C1. A single Kekulé structure does to completely describe the actual bonding in a molecule.

Question 32

Closed-shell electron configuration

Answer 32

Stable electron configuration in which all the lowest energy orbitals of an atom (in the case of the noble gases), an ion (e.g. Na+), or a molecule (e.g. benzene) are filled.

Question 33

ortho-

Answer 33

Term describing a 1,2 relationship between substituents on a benzene ring.

Question 34

meta-

Answer 34

Term describing a 1,3 relationship between substituents on a benzene ring.

Question 35

para-

Answer 35

Term describing a 1,4 relationship between substituents on a benzene ring.

Question 36

phenyl

Answer 36

A benzene ring with 5 hydrogens and 1 methyl or R-group attached. It is often abbreviated C6H5–.

Question 37

benzyl group

Answer 37

The group C6H5CH2–.

Question 38

polycyclic aromatic hydrocarbon

Answer 38

An aromatic hydrocarbon characterized by the presence of two or more fused benzene rings.

Question 39

Birch reduction

Answer 39

Reduction of an aromatic ring to a 1,4-cyclohexadiene on treatment with a group 1 metal (Li, Na, K) and an alcohol in liquid ammonia.

Question 40

Frost circle

Answer 40

A mnemonic that gives the Hückel pi molecular orbitals for cyclic conjugated molecules and ions.

Question 41

annulene

Answer 41

Monocyclic hydrocarbon characterized by a completely conjugated system of double bonds. Annulenes may or may not be aromatic.

Question 42

[x]annulene

Answer 42

An annulene in which the ring contains x carbons.

Question 43

heterocyclic compounds

Answer 43

Cyclic compound in which one or more of the atoms in the ring are elements other than carbon. Heterocyclic compounds may or may not be aromatic.

Question 44

heterocyclic aromatic compounds

Answer 44

A heterocyclic compound in which the ring that contains the heteroatom is aromatic.