18A.3 Flashcards
What is a substitution reaction
a reaction in which an atom, or a group of atoms, in a molecule is replaced by another atom, or a group of atoms
what is an electrophilic reaction
a reaction mechanism in which the attacking species is an electrophile
the benzene ring is
electron rich, though it is electrically neutral, the delocalized electrons forming the pi bond above and below the atoms allows benzene to attract electrophiles
what is an electrophile
an atom, molecule, or ion that can accept a pair of electrons
when an electrophile approaches the delocalized pi-bond in benzene what will happen
it attracts two of six electrons, forming a covalent bond with the benzene, this gives a positive intermediate in which one carbon atom is joined to both the electrophile and the hydrogen
when the electrophile forms a covalent bond with 2 of the 6 delocalized electrons in the pi-bond of benzene where no there is only 4 electrons in the bond, how can we represent that
instead of having a full circle we would have two-thirds of a circle
what happens to the intermediate that forms in the electrophilic substitution of Benzene and why
The H that attached to the carbon that’s attached to the electrophile would leave as H+ and the two electrons in the C-H bond that’s been broken would join the remaining 4 electrons and restore the delocalized pi-bond, and the reason this happens is because the stability of the aromatic compound is broken since the circle is broken, so to restore stability we need to restore the bond
What are the 4 steps that are always involved in the electrophilic substitution mechanisms of Benzene
step 1: formation of the electrophile
step 2: electrophile attack
step 3: the product of a aromatic product
step 4: regeneration of the catalyst
what is the mechanism for Bromination of Benzene (include steps)
page 228
what is the mechanism for the nitration of Benzene (include all steps)
step 1: sulfuric acid and nitric acid react together to form NO2+(the nitryl ion or nitronium ion) page 228
for step on of the nitration of benzene Nitric acid acts like a…. and why
it acts like a base as it expects a proton from sulfur and that is because it is a weaker acid as it dissociates less in water (ie ionizes water from little)
what is the mechanism for the alkylation of Benzene (include all steps)
page 228-229
what is the mechanism for the acylation of Benzene (include all steps)
page 229
