An electron pair that is part of an aromatic cycle is not very basic because reaction of such an electron pair cause a loss of aromatic stabilization
Cyclic conjugated molecules have one lowest energy pi MO, followed by pairs of degenerate MOs at increasingly higher energies. If the total number of MOs is even, then there is one highest energy MO and the MOs are arranged symmetrically about zero energy. If the total number of MOs is odd, a degenerate pair of MOs are highest energy and the MOs are arranged so the average of all of the energies is zero. Electrons are arranged in the MOs according to the same rules that are used for electron in AOs.
Huckel's rule states that cyclic, fully conjugated, planar molecules with 4n + 2 pi electrons (n = any integer including zero) are aromatic. Similar molecules with 4n pi electrons are antiaromatic.
Rings with an odd number of carbons can be aromatic or antiaromatic, if they are planar and have a conjugated p orbital on each ring atom. To have an even number of electrons in their odd number of porbitals, these species must be ionic. They must be carbocations or carbanions. Huckel's rule is used to determine whether the species is aromatic or antiaromatic.
An electron pair that is part of an aromatic cycle is not very basic because reaction of such an electron pair cause a loss of aromatic stabilization.
The hydroboration reaction adds H and OH to an alkene with anti-Markovnikov regiochemistry and syn stereochemistry. The product must be racemic because the reactants are not chiral. Thus, both products a and its enantiomer d must be formed.
This is a hydration reaction. H+ adds in the first step to produce a carbocation. Rearrangement of the initial carbocation should always be considered in any reaction that involves a carbocation intermediate. This product would be formed if the initial carbocation does not rearrange. It is a minor product.
Chlorine and bromine add to an alkene with anti stereochemistry. The addition to a cyclic alkene results in a trans orientation of the bromines. However, if the reactant is not chiral, as in this example, the product must be racemic.
The hydroboration reaction adds H and OH to an alkene with anti-Markovnikov regiochemistry and syn stereochemistry. The product must be racemic because the reactants are not chiral.
The Simmons-Smith reaction converts alkenes to cyclopropane derivative
what is the product of this reaction?
Electrophilic aromatic substitution reactions begin by reaction of a pair of pi electrons of the aromatic ring with the electrophile to produce an arenium ion. Removal of a proton from the arenium ion by someweak base that is present restores the aromatic ring and results in the substitution of the electrophile for a hydrogen on the aromatic ring.