An electrophile is an atom or molecule that is attracted to an area of high electron density, such as the pi bonds in aromatic compounds.
"Attack at para or ortho" refers to the mechanism by which an electrophile reacts with an aromatic compound, specifically at the para or ortho positions, which are the positions adjacent to the functional group on the benzene ring.
This is due to the electron-donating nature of the functional group on the benzene ring, which creates a region of high electron density at the para or ortho positions.
This type of reaction can result in the formation of a new functional group at the para or ortho positions, leading to the synthesis of new compounds with different properties and reactivities.
The attack of an electrophile at para or ortho positions can be controlled by using different reaction conditions, such as changing the temperature or the solvent, or by using different substituents on the benzene ring to alter the electron density at these positions.