The part of a sentence "imperative when" is correct and can be used in written English
It can be used to refer to an important moment when action needs to be taken. For example: It is imperative when you see a dangerous situation to take all safety precautions.
The only imperative when it comes to thank-yous, he confides, is to send them.
Having a realistic knowledge of the terrain is imperative when drawing up plans back at the operations command centre.
As far back as the 1970's, the U.S. Administration of Richard Nixon realized this imperative when it made its historic outreach to Beijing.
Mulgan pointed out that innovation only becomes imperative when crisis looms and institutions react to the past rather than tackle problems of the present.
For example, the planes are more imperative when the president makes multiple stops on a trip; for reporters flying commercial, it can be close to impossible to keep up.
Third, and this is perhaps the most important reason, "personal responsibility" is a vain imperative when the whole sensibility of the people has been restructured, in order to make them receptive to the buying of more and more things.
Because each side has a variety of plausible strategic imperatives when it comes to fiscal policy – and they don't necessarily yield the same policy preferences.
But new-age gerunds give way to old-fashioned imperatives when the professor hands off to the probation officer: good cop, bad cop.
This is especially imperative today, when the executive branch has been making unprecedented claims about the scope of presidential authority.
She was desperate to find something, said it was imperative, but when questioned, couldn't be more specific.
She's desperate to find something, says it's imperative, but when questioned can't be more specific.
