Either C or D. Those r the answers that make more sense.
The Selenium is the element that is likely to be the most brittle
A catalyst is when a chemical reaction occurs faster than normal.
The system is unaffected during a catalyst because both forward and reverse reactions are affected, meaning that quilibrium will occur faster nothing will change.
Hope it helped,
BioTeacher101
Benzaldehyde or C6H5CHO would not undergo the aldol condensation because it does not contain an alpha-hydrogen in its structure. Aldol condensation is a type of reaction that happens between an enolate and an aldehyde or ketone leading to a alkene that has a planar structure. The lack of an alpha-hydrogen would not allow for it to undergo such process since it cannot enolize. Benzaldehyde undergoes a nucleophilic reaction known as Claisen-Schmidt condensation. It has somehow same mechanism of the aldol reaction however, the nucleophilic attack on the carbonyl happens even without the alpha-hydrogen but with an enolate that is from a ketone.