Many electrophilic aromatic halogenations require the presence of aluminum trihalide (halide-chloride or bromide) as a catalyst. Why is it unnecessary to include an aluminum trihalide in the electrophillic aromatic bromination reaction of acetanilide with molecular bromide?

The aluminium trihalide assists in the heterolytic bond fission of the bromine molecule.

Explanation:

The electrophilic aromatic bromination of acetalinide with molecular bromine requires the formation of Br+. This specie is formed when an Aluminum trihalide reacts with bromine. The Br-Br bond breaks heterolytically such that charged species are produced. This Br+ participates in the electrophilic aromatic substitution and AlX4- is formed where X4 shows a tetrahalide complex of aluminium

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.