Introduction to Reactive Intermediates

These flashcards cover key concepts related to the topic of reactive intermediates, including definitions, mechanisms, and factors influencing reactivity.

Reactive intermediates are __ found in shallow dips in the reaction coordinate diagram.

They do not accumulate in solution.

The reaction coordinate maxima represent __ states.

Transition states.

Reactive intermediates are generally __, and under kinetic control.

Irreversible.

For reactive intermediates, if ΔG‡ < ΔG%, then __.

k* > k%.

The reactions of reactive intermediates are usually __, meaning they do not revert back to starting materials easily.

Irreversible.

We will mostly be interested in electron-deficient reactive intermediates like __, carbenes, and nitrenes.

Arynes.

In the early 1950s, unusual reactions were termed __ due to the change in substitution pattern.

Cine-substitutions.

The Roberts experiment provided evidence for the __ mechanism using 14C-labelled chlorobenzene.

Benzyne.

Benzyne has a high-energy __ due to the orientation of exocyclic sp2 hybrids.

HOMO.

Nucleophilic attack susceptibility in benzyne is primarily influenced by the __ of nucleophiles.

Softness.

Regioselectivity in nucleophilic attack on non-symmetrical benzynes is mainly determined by __ effects.

Inductive.

Steric effects can be significant, leading to __ attack to minimise clashes with bulky groups.

Meta.

Early nucleophilic substitutions were influenced by the absence of __ groups.

Electron-withdrawing.

The extent of selectivity in the nucleophilic attack is not always high; sometimes, less control is noted with __ substituents.

Remote.

An elimination-addition mechanism is proposed for reactions where no ortho-H leads to __ products.

Starting material retained.

Formal insertion into C−C bonds of β-ketoesters is a method for synthesizing __ substituted arenes.

Ortho.

Reactions are often driven by co-product stability (ΔH __) and entropic factors (ΔS __).

More negative; more positive.

In benzyne, __ nucleophiles add effectively to it due to LUMO characteristics.

C-nucleophiles.

Kobayashi reagents are useful for __ reactions involving strained alkynes and cyclic allenes.

Diels-Alder.