The Mechanism of the Reaction of Silver Nitrite with Alkyl Halides. The Contrasting Reactions of Silver and Alkali Metal Salts with Alkyl Halides. The Alkylation of Ambident Anions^1,2

Abstract

Dec. 5 , 1955THE ALKYLATION OF AMBIDENT ANIONS 6360 Preparation of the Schiff Base of 9-Anthraldehyde and Racemic 2-hinooctane.-One gram (0.008 mole) of racemic 2-aminooctane, 10 ml. of abs. ethanol and 1.65 g. (0.008 mole) of 9-anthraldehyde refluxed for ten minutes, allowed to come to room temperature and then placed in a refrigerator gave 2.3 g. of product, m.p. 60-62'. When recrystallized from 70% aqueous ethanol it yielded 2.1 g. (83% yield) of yellow crystals, m.p. 61-62'. Anal. Calcd. for QrHwN: C, 87.0; H, 4.41; N, 8.51. Found: C, 87.0; H, 4.37; N, 8.51.Catalvtic Reduction of (+ )a-Phenvlnitr0ethane.-A solution of 6.0 g. (0.40 mo1e)'of '( +) a-phenylnitroethane (b.p: 92' (2 mm.), nZoD 1.5216, az7D $2.80') in 30 ml. of glacial acetic acid was reduced at 4 atm. (1.0 g. of Adams platinum oxide). The theoretical amount of hydrogen was absorbed in 18 minutes and there was obtained 2.8 g. (58% yield) of (+)a-phenylettylamine, b.p. 71-72" (10 mm.), ? z Z o~ 1.5269, a z 7 D $6.50 . This gave the benzamide; recrystallized from absolute ethanol (m.p. 124-125') and then from petroleum ether (b.p. 60-70'); m.p. 124125'; lit. values: ( 7)benzamide deriv., m.p. 124.5-125.516; racemic benzamide of a-phenylethylamine has m.p. 120°.18The reaction of silver nitrite with alkyl halides proceeds via a transition state which has both S N 1 and S N~ character in proportions that vary gradually with the structure of the halide. The products of the reaction reflect this variation in character: The greater the carbonium contribution to the transition state the greater is the yield of nitrite ester and the smaller is the yield of nitroparaffin. This preference of a n anion (Nos-) for covalency formation a t the atom of higher electronegativity (oxygen) is general and forms the basis of the contrasting reactions of silver salts and alkali metal salts (e.g., AgCN and NaCN) with alkyl halides. Electrophilic attack by silver on the halogen of the alkyl halide greatly enhances the carbonium contribution to the transition state and this results in a preference for covalency formation to the most electronegative atom of the anion.Changes in the reaction medium and in the structure of the alkylating agent also may have a profound effect on the nature of the transition state and, when this happens, the nature of the products changes. The following generalization about the alkylation of anions possessing two different reactive positions (Le., ambident anions), which is fully applicable even when silver is absent, provides a simple rationale for the hitherto unsolved problem of carbon 2's. oxygen alkylation, oxygen ws. nitrogen alkylation. etc., in anions derived from acetoacetic ester, phenols, nitroparaffins, or-pyridone, acid amides, thioamides, etc. : The greater the S N 1 character of the transition state the greater is the preference for covalency formation with the atom of higher electronegativity and, conversely, the greater the Sx2 contribution to the transition state the greater the preference for bond formation to the atom of lower...

Nucleophilic properties of purine bases: inherent reactivity versus reaction conditions

“…1,2). In this respect, hard and soft acids and bases (HSAB) theory [12,13] is often invoked along with the empirical Kornblum's rule [14] and Klopman's model of charge-and orbital-controlled reactions [15]. The other sources are connected with various specific interactions between the reagents and/or the environment.…”

N- vs. O-alkylation on 4,6-Dimethyl-2-oxo/Thio-nicotinonitrile

“…3-cyano-4,6-dimethyl-2-thio pyridone (2) towards a number of factors known to have influence in other ambident anion systems. [13][14][15][16] Factors such as solvent, leaving groups, bases and alkyl halide structure were systematically varied during the reaction (Scheme 1 and 2). Table 1 summarizes the data which show the influence of alkylating agent, base and solvent in determining the reaction site in compound 1 while Table 2 shows the similar summarized data for compound 2.…”

“…Several authors 7,8 have discussed the formation of N vs. O alkylation product on pyridone but a reliable assessment of the factors which govern product distribution was limited by the absence of a sufficient body of comparable data. Alkylation on 2-pyridone 9 is influenced by steric factors to result the formation of O-alkylated or N-alkylated product but it has been illustrated that oxygen alkylation was favored when a methyl group occupied the 6-position of 2-pyridone and bulky alkylating agents were employed.…”

Structures of Energetic Acetylene Derivatives HC≡CCH2ONO2, (NO2)3CCH2C≡CCH2C(NO2)3 and Trinitroethane, (NO2)3CCH3

“…The progress and extent of the formation of 2 and 3 can be conveniently followed by filtering and weighing the precipitated silver halides. Previous kinetic and mechanistic investigations of silver salts with alkyl halides have supported a mechanism which has both S N 1 and S N 2 character [23,40]. The alkylation can proceed in two directions, either by Cor O-alkylation.…”