Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Bucherer Reaction
The Bucherer reaction in organic chemistry is the reversible conversion of a naphthol to a
naphthylamine in the presence of ammonia and sodium bisulfite
2C10H7-OH + NH3 ⇌ 2C10H7-NH2 + H2O
The German chemist Hans Theodor Bucherer (1869–1949) discovered (independent from Lepetit) its
reversibility
...


Mechanism
In the first step of the reaction mechanism a proton adds to a carbon atom with high electron
density therefore by preference to C2 or C4 of naphthol (1)
...
In
the next step a bisulfite anion adds to C3 through 1e
...
A nucleophilic addition follows
of the amine with formation of 4a and its tautomer 4b loses water to form the resonance stabilized
cation 5a
...
The enamine eliminates sodium bisulfite with formation of
naphthylamine 6
...
The reaction is summarized as follows

The Bucherer carbazole synthesis is a related reaction
Rosenmund Reduction Mechanism
Rosenmund reaction is a hydrogenation process where molecular hydrogen reacts
with the acyl chloride in the presence of catalyst – palladium on barium sulfate
...

An example of this catalytic hydrogenation of acyl chlorides forming aldehydes is
shown below
...
This leads to the formation of alcohol which further generates an
alkane

Step 3
product is obtained
...
An
example of the method to totally deactivate the palladium over barium sulfate
catalyst is shown below
The Rosenmund catalyst is poisoned to stop further reduction once the desired

Grunwald–Winstein equation
The Grunwald–Winstein equation is a linear free energy relationship between relative rate constants
and the ionizing power of various solvent systems, describing the effect of solvent as nucleophile on
different substrates
...
The
parameter m is a parameter measuring the sensitivity of the solvolysis rate with respect to Y, the
measure of ionizing power of the solvent
The Hammett equation (Equation 1) provides the relationship between the substituent on the
benzene ring and the ionizing rate constant of the reaction
...
This
relationship can be visualized through a Hammett plot
...
Following this idea, Grunwald and Winstein plotted the relative rate constant
vs
...
Since the equation has the same pattern as the Hammett equation but captures the
change of the solvent system, it is considered as an extension of the Hammett equation
...
The first step,
ionizing step, is the rate determining step, SO stands for the nucleophilic solvent
...
Both of them can carry out the nucleophilic
attack on the carbocation
The S 1 reaction is performed through a stable carbocation intermediate, the more nucleophilic
solvent can stabilize the carbocation better, thus the rate constant of the reaction could be
larger
N

m values
The equation parameter m, called the sensitivity factor of solvolysis, describes the
compound’s ability to form the carbocation intermediate in given solvent system
...

If the compounds are not so sensitive to the ionizing ability of solvent, then
the m values are smaller than 1
...
m ≥ 1, the reactions proceed through S 1 mechanism
...
m < 1, the reactions proceed through a mechanism between S 1 and S 2
...
The
combinations are limited to certain systems and only to nucleophilic solvents
...
For many reactions and nucleophilic solvent systems, the relationships are not fully linear
...




---