Answer:
Generally, it is always difficult, requiring a large amount of energy to extract electrons from a 2C compound like acetyl CoA, because they are held closer to the nucleus. Therefore C02 production is difficult. However, in compounds with more than 2C atoms it is easier because the attractive forces of the nucleus on the electrons are reduced, and removal of electrons for C02 production will be easy.
Therefore, it is logical to add 2C acetyl CoA to 4C oxaloacetate to form 6C-Citrate, and electrons extracted for C02 molecules liberation as 6C-succinate is converted to 5C-alpha-ketoglutaric and when the latter compound is converted to 4C-succinate. These are many Carbon compounds with easy electrons loss for the liberation of C02 in sequence.
The above steps will be easier than the direct oxidation of 2C acetyl CoA to liberate two molecules of C02.
Explanation: