# Why add NaBH4 slowly to 4-t-butylcyclohexanone in ether solution? [Lab Procedure]

$\ce{NaBH4}$ is to be added slowly to 4-t-butylcyclcohexanone in ether solution according to laboratory procedures, but I am curious as to why that is? 4-t-butylcyclohexanone undergoes reduction with $\ce{NaBH4}$, so is the reason behind adding NaBH4 slowly to ensure maximum product formation, or is there some safety concern behind this?

• Are you sure this is $\ce{NaBH4}$ or it is really $\ce{LiAlH4}$? – Mathew Mahindaratne Aug 16 '18 at 1:01
• I am sure it is NaBH4 – Jon Aug 16 '18 at 1:04
• "adding NaBH4 slowly to ensure maximum product formation" why would slow addition give higher turnover? – Karl Aug 16 '18 at 5:56
• It's generally good practice to add reagents slowly to prevent thermal runaway in exothermic reactions (where the heat given out by the reaction acts to accelerate it further, creating a feedback loop). Your reaction is in Et2O (B.P. 35C) so even a small exotherm would boil your solvent, hence the slow addition. – PCK Aug 16 '18 at 7:14
• @PCK it is also good practice to render good answers as answers, like your comment above should be one. Thanks! – Oscar Lanzi Aug 16 '18 at 9:56