Organic chemistry reactions happen because electrons are not shared evenly in a chemical bond. Some atoms or molecules, like oxygen, nitrogen, and negatively charged anions, are nucleophilic because they have extra electrons and want to be around positive charges. Others, such as H+ and other positively charged cations, are electrophilic and want to be around negative charges. When an organic molecule has a positive charge, it is called a carbocation. It is also an electrophile. When nucleophiles and electrophiles mix, a reaction can occur. 