Instructor Supplemental Solutions to Problems
© 2010 Roberts and Company Publishers
The Chemistry of Aryl Halides,
Vinylic Halides, and Phenols.
Solutions to In-Text Problems
1-Bromocyclohexene, a vinylic halide, does not react by the S
2 mechanism; 1-(bromomethyl)cyclohexene,
an allylic halide, reacts most rapidly.
(See text Sec. 17.4, text p. 802.)
The reactivity order is
The reaction of compound
is slowest because vinylic halides are
virtually inert in S
1 reactions; and the reaction of compound
is fastest because its ionization gives a
resonance-stabilized allylic carbocation.
The product results from nucleophilic aromatic substitution by the thiolate group:
The second compound,
-fluoronitrobenzene, reacts most rapidly because only in the reaction of this
compound is the intermediate Meisenheimer complex stabilized by resonance interaction of an unshared
electron pair with the nitro substituent.
ligands are L-type ligands; hence, there are no X-type ligands, and, because the charge on Pd is 0,
the oxidation state of Pd is 0.
You might be wondering about the prefix
in the name of this complex.
are used as numerical prefixes instead of
when the group
that is enumerated itself contains multiple substituents.
Thus, the ligand triphenylphosphine
has three phenyl groups on the phosphorus (thus the prefix
in the name of this ligand).
There are four triphenylphosphine ligands—thus the prefix
Pd has ten valence electrons in the neutral atom.
There are no charges and no X-type ligands in the complex;
hence, this is a
Using Eq. 18.24, text p. 836, with an oxidation state of 0, we get the same
Neutral iron (Fe) has 8 electrons.
Because CO is an L-type ligand, it is counted twice in the electron count.
simply solve for
in 8 + 2
= 18 and obtain
, or pentacarbonyliron(0), is in fact a stable complex that
can be purchased commercially.