Diazoalkanes are ambiphilic molecules that may react with electrophiles at carbon to give diazonium ions, with nucleophiles at nitrogen to yield azo compounds, or with dipolarophiles to produce pyrazolines. By studying the kinetics of the reactions of methyl diazoacetate and dimethyl diazomalonate with benzhydrylium ions (Ar2CH+) of known electrophilicity E, we determined their one-bond nucleophilicity parameters N and s N using the equation lg k 2(20 degrees C) = s N(N + E) (eq. (1)). Similarly, the electrophilicity parameters E of these diazoesters were obtained by measuring the rate constants of their reactions with one-bond nucleophiles of known N and s N. These reactivity parameters enable the calculation of rate constants for 1,3-dipolar cycloadditions with dipolarophiles, which proceed stepwise with rate-determining formation of zwitterionic intermediates. Concerted cycloadditions proceed faster than calculated by eq. (1), and the difference between the observed rate constants (Delta G double dagger exptl) and those calculated by eq. (1) (Delta G double dagger eq. 1) gives the energy of concert (Delta G double dagger concert = Delta G double dagger eq. 1 - Delta G double dagger exptl). Contrary to earlier reports, cycloadditions of methyl diazoacetate and dimethyl diazomalonate with enamines proceed stepwise through initial azo couplings. This involves enamine attack at the pi*(N=N) orbital of the diazoalkane, oriented perpendicularly to the commonly considered 3-center 4-electron pi-system. Since this orbital was previously ignored, the common FMO analysis of the reactions of 1,3-dipoles of the propargyl anion type requires revision. A new ordering system for 1,3-dipolar cycloadditions is proposed.

Keteniminium triflates (R2C=C=NMe2+ TfO-) react via classical electrophilic aromatic substitutions with electron-rich arenes forming Wheland intermediates that rapidly undergo triflate-catalyzed tautomerizations to enammonium ions. These ions do not isomerize to the thermodynamically more-stable iminium ions and can quantitatively be converted into the corresponding enamines by treatment with triethylamine. Kinetic studies of keteniminium attack at the arenes provided the electrophilicity parameters of the keteniminium ions E = -2.8 (for R = Me) and E = -1.9 (for R = Ph). These values quantify the one-bond electrophilic reactivity of keteniminium ions and allow us to derive the energy of concert of their [2 + 2]-cycloadditions with alkenes.

Kinetics of the reactions of colored carbanions (reference nucleophiles) with S-(trifluoromethyl)dibenzothiophenium ions (Umemoto's reagents) and hypervalent trifluoromethyl-substituted iodine compounds (Togni's reagents) have been determined photometrically using stopped-flow techniques. The second-order rate constants k2(20 degrees C) for the reactions of Umemoto's sulfonium ions (generation I and II) with the reference nucleophiles in DMSO follow the correlation lg k2(20 degrees C)=sN(N+E) and can be used to determine the electrophilicity parameters E of these trifluoromethylating reagents. It is shown that the conditions reported for the reactions of Umemoto's generation I reagents with a variety of C-nucleophiles are in line with the electrophilicity parameter E approximate to-13 determined for these reagents. Though Togni's hypervalent iodine-based trifluoromethylation reagents do not follow this linear free energy relationship, the kinetics of their reactions with carbanions indicate that they cover the same reactivity range as Umemoto's generation I and II reagents. The second-order rate constants for the reactions of Umemoto's reagents I (X=H) and II (X=F) with carbanions follow the correlation lg k2=sN(N+E) and allow to calculate their electrophilic reactivity parameters E. The reactivities of Togni's hypervalent iodine-based CF3 transfer reagents do not follow this correlation. image

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.

This Glossary contains definitions, explanatory notes, and sources for terms used in physical organic chemistry. Its aim is to provide guidance on the terminology of physical organic chemistry, with a view to achieving a consensus on the meaning and applicability of useful terms and the abandonment of unsatisfactory ones. Owing to the substantial progress in the field, this 2021 revision of the Glossary is much expanded relative to the previous edition, and it includes terms from cognate fields.