The initial energy required is usually called an activation barrier.

With enough energy to surmount activation barriers, however, the isomerization is usually very efficient.

If there is a large activation barrier a spontaneous reaction may take a very long time to proceed.

The activation barrier to give double carbonyl insertions is very high, so it does not occur.

Scientists think that molecules need to get kicked over an "activation barrier" before they can break bonds and form new ones.

Often chemical reactions require energy to overcome an activation barrier.

The energy diverted to overcome these activation barriers is transformed into heat.

Kinetically, there exists a low activation barrier to the decomposition reaction.

In "through the barrier" models, a proton or an electron can tunnel through activation barriers.

However, there is no large activation barrier if the reactants are in the first excited state.