Not all electrophiles will form new C-C sigma bonds with terminal alkyne organometallic reagents. Electrophiles without a positive center, like molecular hydrogen (H-H), typically do not react to form these bonds without the help of catalysts like Pt/C or Pd/C.
When a terminal alkyne is converted to an organometallic reagent through deprotonation with a strong base, it can react with various electrophiles to form new C-C sigma bonds. However, not all electrophiles will react in such a way. Generally, electrophiles that are neutral and do not have an easily displaced leaving group, or are nonpolar such as molecular hydrogen (H-H), will not readily form new C-C sigma bonds with terminal alkyne organometallic reagents since there is no positive center to attract the negatively charged carbon of the organometallic reagent.
Nucleophilic addition reactions typically involve a nucleophile attacking an electrophilic center to form a new sigma bond. Lewis acid catalysts like Pt/C or Pd/C are required to facilitate the addition of hydrogen (H-H) to an alkyne. These finely divided metals serve as a surface upon which the reaction can take place, without directly forming a C-C sigma bond between the organometallic alkyne and the hydrogen molecules.
In contrast, a carbonyl carbon (C=O), especially when it's part of a reactive intermediate or in the presence of a strong acid or base, can serve as an electrophile to form a new C-C sigma bond during a nucleophilic addition reaction, given that the nucleophile attacks the electrophilic center of the carbonyl group.
The complete question is- Terminal alkynes (HCCR) can be converted to organometallic reagents through deprotonation with a strong base. Which electrophile shown below WILL NOT result in a new C-C sigma bond during a reaction with a terminal alkyne organometallic reagent?
A. 1-iodopropane
B. 2-iodopropane
OC. Aldehyde
D. Epoxide