Step 1 : Generation^⊕CHFO electrophile:
AlCl₃+CH₃COCl\(\longrightarrow\)^⊕CH³CO+AlCl₄
Step 2 : Attack of the electrophile on benzene ring to form arenium ion

Step3 : Rearomatisation of arenium ion

Step 1 : Generation of ^⊕CH₃electrophile
AlCl3+CH3Cl\(\longrightarrow\)^⊕CH₃+Alcl₄^Ө
Step 2 : Attack of the electrophile on benzene ring to form arenium ion:

Step 3 : Rearomatisation of arenium ion:

Step 1: Generation of S03 electrophile:

Step 2: Attack ofthe electrophile on benzene ring to form arenium ion:

Step 3: Rearomatisation of Arenium ion:

Step 1: Generation of CI+ electrophile.

Step 2: Attack of the electrophile on the benzene ring to form arenium ion:

Step 3: Rearomatisation of arenium ion:

An alkyne shows acidic nature only if it contains terminal hydrogen atom. This can be explained by considering the sp hybrid orbitals of carbon atom in alkynes. The percentage of s-character of sp hybrid orbital (50%) is more than Sp² hybrid orbital ofalkenes (33%) and sp3 hybrid orbital of alkanes (25%). Because of this, carbon atom becomes more electronegative, thus facilitating donation of H+ ions to bases. So hydrogen attached to triply bonded carbon atoms is acidic in nature.
(i) \(\underset { (1-Butyne) }{ CH_{ 3 }-{ CH }_{ 2 }-C } \equiv CH+{ CuCl }_{ 2 }+\underset { (Silver\quad bitynide) }{ { 2NH }_{ 4 }OH } \longrightarrow { CH }_{ 3 }-{ CH }_{ 2 }-C\equiv C-Cu\downarrow 2{ NH }_{ 4 }{ NO }_{ 3 }+2{ H }_{ 2 }O\)(ii) \({ CH }_{ 3 }-{ CH }_{ 2 }-C\equiv CH+{ CuCl }_{ 2 }+2{ NH }_{ 4 }\longrightarrow { CH }_{ 3 }-{ CH }_{ 2 }-C\equiv C-C\downarrow 2{ NH }_{ 4 }{ NO }_{ 3 }+2{ H }_{ 2 }O\)
(iii) 
\(\underset { (2-Butyne) }{ { CH }_{ 3 }-C\equiv C-{ CH }_{ 3 } } +2Ag{ NO }_{ 3 }+2{ NH }_{ 4 }OH+2{ NH }_{ 4 }OH\longrightarrow No\quad reaction\quad due\quad to\quad absence\quad of\quad acidic\quad hydrogen\)