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S_N2 versus S_N2' Competition.

ABSTRACT: We have quantum chemically explored the competition between the S_N2 and S_N2' pathways for X^- + H₂C═CHCH₂Y (X, Y = F, Cl, Br, I) using a combined relativistic density functional theory and coupled-cluster theory approach. Bimolecular nucleophilic substitution reactions at allylic systems, i.e., C^γ═C^β-C^α-Y, bearing a leaving-group at the α-position, proceed either via a direct attack at the α-carbon (S_N2) or via an attack at the γ-carbon, involving a concerted allylic rearrangement (S_N2'), in both cases leading to the expulsion of the leaving-group. Herein, we provide a physically sound model to rationalize under which circumstances a nucleophile will follow either the aliphatic S_N2 or allylic S_N2' pathway. Our activation strain analyses expose the underlying physical factors that steer the S_N2/S_N2' competition and, again, demonstrate that the concepts of a reaction's "characteristic distortivity" and "transition state acidity" provide explanations and design tools for understanding and predicting reactivity trends in organic synthesis.

SUBMITTER: Hansen T

PROVIDER: S-EPMC9295157 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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SN2 versus SN2' Competition.

Hansen Thomas T Vermeeren Pascal P de Jong Lea L Bickelhaupt F Matthias FM Hamlin Trevor A TA

The Journal of organic chemistry 20220624 14

We have quantum chemically explored the competition between the SN2 and SN2' pathways for X- + H2C═CHCH2Y (X, Y = F, Cl, Br, I) using a combined relativistic density functional theory and coupled-cluster theory approach. Bimolecular nucleophilic substitution reactions at allylic systems, i.e., Cγ═Cβ-Cα-Y, bearing a leaving-group at the α-position, proceed either via a direct attack at the α-carbon (SN</s ...[more]

PMID: 35748807

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Project description:This study examined hormonal responses to competition in relation to gender, social context, and implicit motives. Participants (N = 326) were randomly assigned to win or lose in a 10-round, virtual face-to-face competition, in same-sex individual- and team-competition contexts. Saliva samples, taken before and twice after the competition, were assayed for testosterone (T), estradiol (E), progesterone (P), and cortisol (C). Implicit needs for power (nPower) and affiliation (nAffiliation) were assessed with a picture-story exercise before the competition. Aggression was measured via the volume at which participants set noise blasts for their opponents. Men competing individually and women competing as teams showed similar T increases after winning. C was differentially associated with outcome in the team matches, with higher post-match cortisol for winning women, and an opposite effect for male teams. Analyses including implicit motives indicated that situational variables interacted with motivational needs in shaping hormonal responses to competition: in naturally cycling women, nPower predicted T increases after winning and T and E decreases after losing. In men, nPower predicted T increases after losing and decreases after winning. In male teams, nPower predicted C increases after losing, but not after winning, whereas in individual competitions, nPower was a general negative predictor of C changes in women. nAffiliation predicted P increases for women competing as teams, and P decreases for women competing individually. Aggression was higher in men, losers, and teams than in women, winners, and individuals. High aggression was associated with high baseline C in women competing individually and with low baseline C and C decreases in women competing as teams and in men generally. Our findings suggest that while situational and gender factors play a role in hormonal responses to competition, they also depend on their interplay with motivational factors. They also suggest that while aggression is strongly affected by situational factors in the context of a competition, it has no direct association with motivational and hormonal correlates of dominance (nPower, T, E) and instead is associated with (mostly) low levels of C.

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S_N2 versus S_N2' Competition.

Publications

S<sub>N</sub>2 versus S<sub>N</sub>2' Competition.

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