| Home / lib / Ch_Chemistry / | ||
Vogel A.I. Textbook on organic chemistry (1957)(ISBN 0582442451)(T)(1214s).djvu |
|
Size 13.8Mb Date Jan 24, 2005 |
first until the violent reaction subsides, and then with the water boiling
vigorously for 2 hours...
Immediately separate the sulphonyl
chloride from the supernatant liquid by decantation, wash with two 90 ml...
The latter will retain sufficient acid to render unnecessary the
addition of acid in the subsequent reduction with iron...
The experimental conditions necessary for the preparation of a solution of a
diazonium salt, diazotisation of a primary amine, are as follows...
Happily, most of the useful reactions of diazonium com-
compounds can be carried out with the readily-acoessible aqueous solutions, so
that the solid (explosive) diazonium salts are rarely required...
// cannot be too strongly emphasised that in all these reactions violently explosive
diazo sulphides and related compounds may be formed, and another less hazardous
method for the preparation of the desired compound should be used, if possible...
Equip the 2 ¦ 5 litre flask holding the cuprous solution for steam distil-
distillation (Fig...
Diazotisation and reaction with cuprous bromide
yields 2-bromonaphthalene-l-sulphonic acid ; heating with sulphuric acid
eliminates the sulphonic acid group to give 2-bromonaphthalene...
of
water from a separatory funnel taking care that the temperature does
not rise above 10°...
Render the dis-
distillate alkaline with 10 per cent, sodium hydroxide solution (about 50 ml.)
and separate the lower red layer of crude o-bromotoluene...
Continue the cautious heating from time to time
as may be necessary to keep the reaction going...
D) If the reaction becomes too vigorous, it may be necessary to cool the flask
by covering it with a damp cloth...
Collect the pure m-nitro-
phenol at 160-165°/12 mm.; always allow the flask to cool before admitting air
otherwise the residue may decompose with explosive violence...
Collect the pure p-nitrophenylarsonic acid, wash with, small
volumes of ice-cold water, and dry in the steam oven...
If RNH2 contains a sulphonic acid group, the reaction product may be
neutralised and R'NH2 extracted with ether...
The subsequent stages in the preparation—addition of dimethyl-
aniline solution, etc.—are as above...
dropping funnel a glass tube
which dips well below the surface of the solution and is bent upwards at
the end and constricted so that the opening is about 2 mm.; this arrange-
arrangement ensures that the entrance of the acid liquor into the nitrite solution
is prevented...
The process is
by no means a simple one : by the use of milder reducing agents and by the
control of the hydrogen ion concentration (pH) of the solution, a number of
intermediate products may be isolated, some of which are products of direct
reduction and others are formed through secondary changes...
Azoxybenzene is readily prepared by reduction of nitrobenzene in an alkaline
medium with dextrose or sodium arsenite :
0
2C6HBNO2 + 6H —- C6HBN=NC,,H6 + 3H2O
Reduction of nitrobenzene in methyl or ethyl alcoholic sodium hydroxide
solution with zinc powder leads to azobenzene or hydrazobenzene according
to the proportion of zinc powder employed :
2C4H5NO2 + 4Zri + 8NaOH —> C6HBN=NC6H5 + 4Na2[Zn02] + 4H2O
2C,,H6NO2 + 5Zn + lONaOH —> CjHjNHNHCjHs + 5Na2[Zn02] + 4H2O
Hydrazobenzene may be oxidised to azobenzene by sodium hypobromite
solution at 0°...
Continue
the stirring for a further 15 minutes, by which time the reduction is
complete as is shown by the fact that the temperature commences to fall...
| © 2007 eKnigu | ||