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Definition
| A general name for an aromatic hydrocarbon, abbreviated ArH |
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Term
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Definition
| The general name for a group obtained by the removal of a hydrogen from a ring position of an aromatic hydrocarbon, abbreviated Ar- |
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Term
| Electrophilic aromatic substitution |
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Definition
| Replacement of a hydrogen on an aromatic ring by a strong electrophile. Also called SE2 reaction for Substitution, Electrophilic, Bimolecular |
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Definition
| A nonaromatic, resonance-stabilized cyclohexadienyl carbocation inter-mediate that is formed when the pi system of benzene attacks an electrophile. Also called a σ-complex |
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Definition
| Replacement of an aromatic ring hydrogen atom by a halogen atom (F, Cl, Br, or I). |
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Definition
| A compound that is an acid because it is an electron pair acceptor; common examples include AlCl3 , FeBr3 , BF3 , etc. |
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Definition
| Replacement of an aromatic ring hydrogen atom by a nitro group, -NO2 |
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Term
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Definition
| Replacement of an aromatic ring hydrogen atom by a sulfonic acid group, -OSO2H |
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Term
| Friedel-Crafts alkylation |
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Definition
| Formation of an alkyl arene by replacement of an aromatic ring hydrogen atom with an alkyl group, -R , via a carbocation intermediate. |
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Term
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Definition
| A functional group consisting of a carbonyl group, >C=O, attached to an alkyl or aryl group, -C(O)R; it is often added by reaction with a carboxylic acid derivative. Also called an alkanoyl group |
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Term
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Definition
| A general name for an activated carboxylic acid derivative, in which the hydroxyl group of the acid is replaced by a halogen atom, RC(O)X. Also called an acid halide |
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Term
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Definition
| Formation of an acyl arene (aryl ketone) by replacement of an aromatic ring hydrogen atom with an acyl group, -C(O)R , via an acylium ion intermediate |
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Term
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Definition
| The resonance-stabilized cation: R-C+=O ↔ R-C≡O+ . Also called an acyl cation |
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Term
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Definition
| reduction of a carbonyl group to a methylene group by amalgamated zinc, Zn(Hg), in dilute hydrochloric acid, HCl. |
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Term
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Definition
| An effect on the rate of reaction (or on the equilibrium constant) caused by the replacement of a hydrogen atom by another atom or group; effects include those caused by the size of the atom or group, called steric effects, and those effects caused by the ability of the group to withdraw or donate electron density, called electronic effects (inductive effects or resonance effects). |
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Term
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Definition
| A substituent that makes the aromatic ring more reactive than benzene, usually referring to electrophilic aromatic substitution |
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Term
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Definition
| A group that, when present on a benzene ring, directs an incoming electrophile to a position ortho and/or para to itself |
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Term
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Definition
| A substituent that makes the aromatic ring less reactive than benzene, usually referring to electrophilic aromatic substitution |
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Term
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Definition
| A group that when present on a benzene ring, directs an incoming electrophile to a position meta to itself |
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Term
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Definition
| An effect by which a substituent exerts either an electron-donating or electron-withdrawing effect through the pi system of the molecule |
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Term
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Definition
| Polarization of a molecule, due to the effect of a group that is either electron-donating or electron-withdrawing, which is transmitted through space and through the bonds of the molecule, but the effect gets weaker with increasing distance from the group |
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Term
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Definition
| Stabilization of a reactive intermediate by donation or withdrawal of electron density through sigma bonds; i.e., alkyl groups stabilize carbocations and arenium ions through hyperconjugation |
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Term
| Hammond-Leffler Postulate |
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Definition
| In a multistep reaction, the structure of a transition state of a given step will resemble the stable species that is nearest to it in free energy; the transition state of an endergonic step will resemble the products of that step, whereas the transition state of an exergonic step will resemble the reactants of that step |
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Term
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Definition
| Refers to a substituent on the side-chain carbon atom that is directly attached to a benzene ring |
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Term
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Definition
| An unusually stable free radical, in which the side-chain carbon atom that is directly attached to a benzene ring has an unpaired electron, Ph-C ∙ R2 - |
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Term
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Definition
| An unusually stable carbocation, in which the side-chain carbon atom that is directly attached to a benzene ring has a positive charge, Ph-C + R2 - |
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Term
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Definition
| A group that is introduced into a molecule to protect a sensitive group, while the reaction is carried out at some other location in the molecule; the protecting group is later removed in a subsequent reaction |
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Term
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Definition
| A group that is introduced into a molecule to block the reaction at a particular site, such as a carbon atom, while the reaction is carried out at some other location in the molecule; the blocking group is later removed in a subsequent reaction |
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Term
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Definition
| A general term for any carbocation that has a carbon atom with a positive charge that is singly bound to a C=C double bond, with the general formula +CR2-C(R)=CR2 ; substituted allylic cations are more stable than any saturated carbocation due to delocalization of the positive charge through resonance |
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Term
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Definition
| The partial reduction of a benzene ring by sodium or lithium metal in liquid ammonia; the products are usually l,4-cyclohexadienes |
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