Menschutkin reaction stereoselectivities of nicotine and related compounds

Seeman, Jeffrey I.; Secor, Henry V.; Whidby, Jerry F.; Bassfield, Ronald L.

doi:10.1016/s0040-4039(01)94704-5

Cited by 12 publications

(9 citation statements)

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“…( 26) is analogous to the Winstein-Holness eqn. (21), and since K = X3/X2. one can solve for K and derive eqn.…”

Section: Bvi-hmentioning

confidence: 96%

“…Similarly, the ratio fev-.p/^vc -p, 's small (<1) because the methyl iodide must approach trans to the aromatic ring in the Vc -*• reaction but cis to the aromatic ring in the Vt -* Pc reaction. There is thus a counterbalancing of steric effects, the factors which influence K to be large similarly cause kv_.vjkVc .P, to be small (21,22). This balancing of effects is indicated by eqn.…”

Section: A Direct Relationship Between Product Ratio and Conformer Di...mentioning

confidence: 97%

“…(1) system, one can solve for K in terms of k2y, £34, and &w-H from eqn. (21), as shown in eqn. (22), keeping in mind the C-H/W-H requirement that k23, k32 » k2\, 634.…”

Section: A Direct Relationship Between Product Ratio and Conformer Di...mentioning

confidence: 99%

“…Of course, the restrictions on the basis of which eqns. ( 3), ( 6), ( 11), ( 15), (21), and (22) As both the C-H principle and the W-H equation were derived under the assumption of fast conformational interconversions/slow chemical reactions, the C-H/W-H principles are clearly valid only when this assumption is valid. Zefirov (17) in 1977 advanced an exact solution for the product ratio [A<t]/[Ai]" for eqn.…”

Section: Extensions Of the C-h/w-h Conceptsmentioning

confidence: 99%

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The Curtin-Hammett principle and the Winstein-Holness equation: new definition and recent extensions to classical concepts

Seeman¹

1986

J. Chem. Educ.

195

131

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One measure of value of a scientific principle is its frequency and scope of usage. Concepts are frequently developed for specific applications. It will be argued for the cases discussed herein, and perhaps more generally, that the original applications of a particular theory can serve unwittingly as an unfortunate limitation: the full development of the theory may be impeded if the theory is "locked into" its original application by a unidirectional mindset of potential users.The simplest kinetic system which exemplifies the effect of conformation on chemical reactivity is shown in eqn. (1). Here, two different conformations A2 and A3 of the same molecule react with rate constants k2i and k34, respectively, to give two different products, Ai and A4. One can easily envision extensions of eqn. (1) to more complex situations involving conformations, some (or all) of which react to form one or more products. A significant variable is the magnitude of the rate constants for conformational interconversion kc (k23 and k32 in eqn. (1) relative to the rate constants for reactivity kr (k2\ and k34). Because the rates of conformational interconversion are generally, though not invariably, larger than their rates of chemical reactivity, (I), we shall limit ourselves in this and the next four sections below to the Curtin-Hammett/Winstein-Holness conditions, namely kc » kr (hi3, k32 » k2i, k34 in eqn. (1).

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“…( 26) is analogous to the Winstein-Holness eqn. (21), and since K = X3/X2. one can solve for K and derive eqn.…”

Section: Bvi-hmentioning

confidence: 96%

Section: A Direct Relationship Between Product Ratio and Conformer Di...mentioning

confidence: 97%

“…(1) system, one can solve for K in terms of k2y, £34, and &w-H from eqn. (21), as shown in eqn. (22), keeping in mind the C-H/W-H requirement that k23, k32 » k2\, 634.…”

Section: A Direct Relationship Between Product Ratio and Conformer Di...mentioning

confidence: 99%

Section: Extensions Of the C-h/w-h Conceptsmentioning

confidence: 99%

See 2 more Smart Citations

The Curtin-Hammett principle and the Winstein-Holness equation: new definition and recent extensions to classical concepts

Seeman¹

1986

J. Chem. Educ.

195

131

View full text Add to dashboard Cite

show abstract

“…We have shown (3,6) that treatment of nicotine with less than one equivalent of iodomethane leads to both N'-methylnicotinium iodide and Nmethylnicotinium iodide in a ratio of 2.2:l even though nicotine's pyrrolidine nitrogen is considerably more basic than its pyridine nitrogen (pKa 7.8, pK 3.04). In addition, we observed that iodomethylation of nicotine with one equivalent of iodomethane results in dialkylation products and unreacted starting material (3,6). These three suggestions may explain reports of low nicotine yields on iodomethylation of nornicotine (4b, 4d, 4e, 5).…”

Section: Resultsmentioning

confidence: 93%