CHEM 2580 Chapter 15: Benzene and Aromaticity Flashcards

Vocabulary practice flashcards generated from CHEM 2580 Chapter 15 notes covering benzene structure, aromaticity rules, nomenclature, and key biochemical examples.

Firefly Luciferin

A compound that reacts with enzymes found in fireflies to emit light through chemiluminescence, also found in other light-emitting insects such as the railroad worm, starworm, and click-beetle.

Resonance Hybrid

The actual structure representing a combination of imaginary individual resonance forms; it does not alternate between forms and is more stable than any individual resonance form.

Cinnamaldehyde

A phenylpropanoid responsible for the flavor and odor of cinnamon, which is naturally synthesized by the shikimate pathway in bacteria, fungi, and protozoa.

Phenylalanine

An amino acid that the human body cannot synthesize on its own and must obtain from food; it is converted into tyrosine to synthesize the neurotransmitters dopamine and norepinephrine.

Acetaminophen

A medicinal compound that functions as an analgesic and antipyretic.

Benzene C-C Bond Length

All carbon–carbon bonds in benzene are identical in length at $139\,pm$, placing them between a standard carbon–carbon single bond ($154\,pm$) and double bond ($134\,pm$).

Electrophilic Aromatic Substitution (EASy)

The characteristic reaction type of benzene, wherein it undergoes substitution rather than addition reactions due to the special stability and low reactivity of its $\pi$ bonds.

Monosubstituted Benzenes

Benzene rings containing a single substituent, systematically named using -benzene as the parent suffix (e.g., Bromobenzene, Nitrobenzene).

Ortho, Meta, Para (OMP) Designations

Nomenclature prefixes used for disubstituted benzenes based on substituent position: Ortho ($o$) for 1,2 and 1,6; Meta ($m$) for 1,3 and 1,5; and Para ($p$) for 1,6.

Arenes

Alkyl-substituted benzenes.

Phenyl Group

A substituent benzene ring represented as $-C_6H_5$ (abbreviated as Ph or $\Phi$).

Benzyl Group

A substituent group consisting of a benzene ring attached to a methylene group, represented as $C_6H_5CH_2-$.

Hückel 4n + 2 Rule

A rule developed by Erich Hückel in 1931 stating that a molecule is aromatic if it is planar, cyclic, has overlapping $\pi$ bonds or $p$ orbitals, and contains $4n + 2$ $\pi$ electrons ($2e^-$, $6e^-$, $10e^-$, etc., where $n = 0, 1, 2, 3\dots$).

Anti-aromaticity (Hückel 4n Rule)

A property of unstable, difficult-to-isolate molecules that are planar, cyclic, fully conjugated, and contain $4n$ $\pi$ electrons ($4e^-$, $8e^-$, $12e^-$, $16e^-$, etc.); such compounds often distort from planar geometry to avoid anti-aromaticity.

Heteroatom Lone Pair Rule for Heterocycles

A rule used to determine aromaticity in heterocycles stating that if the heteroatom is not part of a double bond, count one lone pair toward the $4n + 2$ Hückel rule.

Planar Aromatic Ions

Carbocations or carboanions that are planar and possess $2\pi$ or $6\pi$ electrons satisfying Hückel's rule, allowing them to form more rapidly than non-aromatic ions.