FG Classification Rules. In the proposed classification scheme the following rules are followed in the assignment of class designations to functional groups Activating functions are to be considered as heteroatoms appended to or included within the carbon skeleton Activating functions are inspected and classified according to their observed polar site reactivi- Since both proton removals and addition processes are frequently an integral component in functional group activation, the function, its conjugate acid or base, and its possible proton tautomers are considered together in determining its class designation The oxidation state of the FG is de-emphasized since this is a subordinate strategic considera E-Functions. For example, carbonyls and carbonyl derivatives will be represented as=X where X lay be either oxygen or substituted nitrogen. Well recognized exceptions to the polar class designations illustrated in Scheme I may be found in the chemistry of CO and HCN. In these instances the carbon bearing the heteroatom exhibits well-defined nucleophilic properties. Accordingly these two functional Table I. Common E-Functions: Symbolf+)C-E NR2 =NR exception X, X= halogen Also consider all combinations of of above FGs: e.g=0+ OR G-Functions. Typical G-class functions are the Group I-IV metals whose reactivity pattern, falls into a subset of 7 H2C-CH-CH2-Li CH3 CH2-MgBr tnnenA-Functions. A-functions are usually more structurally complex FGs composed of polyatomIc plages of nitrogen, oxygen and their heavier Group V and VI relatives(P, As, S, Se). Typical A functions, classified by inspection, are provided in Table II Table IL. Common A-Functions: Symbolt)C-A 一NO2=NR=NR=NOR=三N so2 R P(O)R2 --PR3 Functional groups possessing the following general structure, =N-X where X is a hetroatom oofectrops nonbonding electron pair, have an expanded set of resonance options which create either an ilic or nucleophilic potential at the point of attachment. Remarkably, the dual electronic pro oximes were first discussed by Lapworth2 in 1924 before the modern concepts of valence bond develo These FG's are capable of conferring both(+)and(-)at the point of attachme OR, NR 2)Lapworth, A Chemistry and Industry 1924, 43, 1294-1295Functional Group Classification page 5 FG Classification Rules. In the proposed classification scheme the following rules are followed in the assignment of class designations to functional groups. ■ Activating functions are to be considered as heteroatoms appended to or included within the carbon skeleton. ■ Activating functions are inspected and classified according to their observed polar site reactivi￾ties. ■ Since both proton removals and addition processes are frequently an integral component in functional group activation, the function, its conjugate acid or base, and its possible proton tautomers are considered together in determining its class designation. ■ The oxidation state of the FG is de-emphasized since this is a subordinate strategic considera￾tion. E-Functions. For example, carbonyls and carbonyl derivatives will be represented as =X where X may be either oxygen or substituted nitrogen. Well recognized exceptions to the polar class designations illustrated in Scheme I may be found in the chemistry of CO and HCN. In these instances the carbon bearing the heteroatom exhibits well-defined nucleophilic properties. Accordingly these two functional groups will be classified as A-functions by inspection (vide infra). OR O O C E NR2 NR N X, X = halogen Also consider all combinations of of above FGs; e.g =O + OR exception: exception: Table I. Common E-Functions: Symbol: (+) G-Functions. Typical G-class functions are the Group I-IV metals whose reactivity pattern, falls into a subset of 7. H2C CH CH2 Li C C C G CH3 CH2 MgBr (–) (+) (–) (–) (–) (–) 7 A-Functions. A-functions are usually more structurally complex FGs composed of polyatomic assemblages of nitrogen, oxygen and their heavier Group V and VI relatives (P, As, S, Se). Typical A￾functions, classified by inspection, are provided in Table II. NO2 NOR C A SR PR2 P(O)R2 NNR2 N(O)R N2 N S(O)R SO2R SR2 PR3 + + Table II. Common A-Functions: Symbol: (±) Functional groups possessing the following general structure, =N-X where X is a hetroatom bearing a nonbonding electron pair, have an expanded set of resonance options which create either an electrophilic or nucleophilic potential at the point of attachment. Remarkably, the dual electronic properties of oximes were first discussed by Lapworth12 in 1924 before the modern concepts of valence bond reso￾nance was developed. R H N X: R H N X: R H N X: ■ These FG's are capable of conferring both (+) and (–) at the point of attachment. (+) (+) (–) (–) X = OR, NR2 12) Lapworth, A. Chemistry and Industry 1924, 43, 1294-1295