Organic 11: Arenes & Aromaticity

Question 1

Arenes

Answer 1

hydrocarbons based on the benzene ring as a structural unit; ex. benzene, toluene, naphthalene; AKA aromatic hydrocarbons

Question 2

Aromaticity

Answer 2

special stability associated with aromatic compounds

Question 3

Aliphatic hydrocarbons

Answer 3

alkanes, alkenes, and alkynes belong to this class; name given to hydrocarbons that were obtained by the chemical degradation of fats

Question 4

Kekule (accented final e) structure

Answer 4

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; two formulations for benzene are 1, 2 and 1, 6 disub’d; a single structure does not completely describe the actual bonding in the molecule

Question 5

Resonance energy

Answer 5

extent to which a substance is stabilized by electron delocalization; it is the difference between the substance and a hypothetical model in which the electrons are localized

Question 6

Closed-shell electron configuration

Answer 6

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 7

Xylenes

Answer 7

dimethyl derivatives of benzene; 3 isomers: ortho-, meta-, and para-

Question 8

Ortho-

Answer 8

prefix signifying a 1,2-disubstituted benzene ring

Question 9

Meta-

Answer 9

prefix signifying a 1,3-disubstituted benzene ring

Question 10

Para-

Answer 10

prefix signifying a 1,4-disubstituted benzene ring

Question 11

Phenyl-

Answer 11

when the benzene ring is named as a substituent, this word stands for C6H5-

Question 12

Aryl group

Answer 12

an arene named as a substituent

Question 13

Benzyl group

Answer 13

C6H5CH2-

Question 14

Polycyclic aromatic hydrocarbons

Answer 14

members of this class of arenes possess substantial resonance energies because each is a collection of benzene rings fused together

Question 15

Carcinogen

Answer 15

cancer-causing substance; ex. benzo[a]pyrene

Question 16

Buckminsterfullerene

Answer 16

name given to the C60 cluster with structure resembling the geodesic domes of R. Buckminster Fuller

Question 17

Electrophilic aromatic substitution

Answer 17

most important reaction type exhibited by benzene and its derivatives

Question 18

Benzylic carbon

Answer 18

a carbon atom that is directly attached to a benzene ring

Question 19

Birch reductions

Answer 19

metal-ammonia-alcohol reductions of aromatic rings

Question 20

Anti-aromatic molecules

Answer 20

molecules that are destabilized by delocalization of their pi electrons

Question 21

Huckel’s Rule

Answer 21

among planar, monocyclic, fully conjugated polyenes, only those possessing (4n + 2) pi electrons, where n is a whole number, will have special stability, that is, be aromatic

Question 22

Frost Circle

Answer 22

a mnemonic that gives the Huckel pi MOs for cyclic conjugated molecules and ions

Question 23

Annulene

Answer 23

refers to completely conjugated monocyclic hydrocarbons with more than 6 carbons

Question 24

[x]annulene

Answer 24

higher members of the annulene group, where x is the number of carbons in the ring

Question 25

Heterocyclic compounds

Answer 25

cyclic compounds that contain at least 1 atom other than carbon within their ring

Question 26

Heterocyclic aromatic compounds

Answer 26

cyclic compounds that contain at least 1 atom other than carbon within their ring and possess aromatic stability