ISSUE:

In the alkylation of a carbonyl compound, the first stage consists of the deprotonation of said compound using a strong base, such as LDA.

In the manual that I am following, it is indicated that enolization occurs through the following cyclical mechanism:



Looking at the mechanism, I have the following questions:
- How do the electrons move? I don't know very well how the pair of electrons of the LDA intervenes.
- Why is it necessary to use THF as a solvent and a temperature of -78 ºC?

Thank you very much in advance.

Hi, Nitrogen has a lone pair with which it captures the alpha hydrogen of the ketone, forming diisopropylamine.

The CH bond becomes a CC double bond and the CO double bond breaks, passing its electrons to oxygen as a lone pair. Lithium remains in the middle as a lithium cation and binds to negative oxygen in the form of an ionic bond. LDA is a very strong base and cannot be dissolved in protic solvents (water or alcohols) as it deprotonates them.
For this reason it should always go in ethereal solvents. Low temperature favors elimination reactions over substitution reactions. I send you a greeting.