chemical physics of discharges - Argonne National Laboratory
chemical physics of discharges - Argonne National Laboratory chemical physics of discharges - Argonne National Laboratory
270 R .ACTION OF 'bI.4LEI.C J.NI?Y?'lRITE WITH ARCFl;\TTC FT'rllRCC.4IIRDNS UKDER TIi5 INFZUXNCE OF SILENT ZL'XTRIC ?ISC?!.RGX A.T ATWSPHTRIC F'RZSSVRRE. Stylianos Sifniades, David Jerolamcn, Robert Fuhrmam' Allied Chemical Ccrporation, Central Research Laboratory, Box 309, Yorristown, N. 3. I Maleic anhydride is lmoyn to form two olasses of adducts with alkyl benzenes, depending on the conditions of excitation. A t reflux . t-peratures and in the presence of. catalytic amounts of peroxides adducts of type'I 2re formed (1,2). A free radical chain reaction is assumed involving abstraction of a benzylic hydrogen. The chain length, based on the ratio of product to' added peroxide, is 20 to 100. R I (R,Rf = II or Me; R"= Me,Et,i-Pr) I1 (R,Rf= H,Me,t-Ru,Cl) 4t FGOIU or somewhat higher temperatures and in the presence of ultra-violet radiation aPducts of type I1 are formed (3 to 8). Excited aromatic molecules or excited charge-transfer complexes of maleic anhydride with an aromatic molecule are claimed tc be the reaction intermediates. The addition is sensitized by benzophenone, but the adduct can be formed in the absence of a sensitizer, although at a much lower rate. It appears that the presence of benzophenone is. iridis- pensable if sun light is used as the source of exciting radiation (9). It is interesting to note that in this case only benzene forms an adhct IT with maleic anhydride, while alkylbenzenes are only partly Incorporated in poly-anhydride chains which are formed. Recently formation of the adduct I1 of benzene and maleic anhydride 'under the influence of gamma radiation was reported (10). The adduct is only a minor product ,of the reaction, corresponding to about 4% of the maleic anhydride spent. The main product is a mixture of polyanhydrides. These can be considered to arise through a free radical chain similar to the one yielding adducts of type I. It is then clear that in the system maleic anhydride-benzene (6r alkylbenzene) two types of reactions are prevalent, one by free radical chain yielding adduct T or poly-anhydrides, the other by means of excited molecules or charge-transfer complexes yielding adduct II. It was thought of interest to investigate the influence of silent or corona discharge on this system. This type of discharge was chosen because it is easy to maintain at atmospheric pressure. -iharge apparatus was essentially a modif led Siemens ozonizer Vertically mounted. It was made of Pyrex glass. A solution of sodium chloride in glycerol circulating in the jacket constituted the ground electrode, while a silver coating In the interior surface of the central
271 tube serve? as the high voltare electrode. The action mixture was circulated at a hi-h rate from top Lo bottom through the reactor by means of a custom-made membrane pump constructed of Halon (registered mark of Allied Chemical Corooration). $n inert gas, nitrogen or helium, was introdwed at the top of the reactor and vented at the bottom through a condenser. The temwerature of the reaction mixture was measured at the exit of the discharpe. Temaerature control was ensured by regulating the temperature of the circulating glycerol solution. I Current at the desired frequencies was produced by an audiofrequency generator (Heathkit ?lode1 17-71?) cou2led with a 1000 VA custom-madeamdifier. It was raised to high voltage by means of a 25 KV transformer. Lower voltages could be obtained by acting on the outgut of the avlifier. The power input to the system was monitorcd by nekns of a watt-meter (Westinphouse Type PYb, specially compensated for high frequency work) at the primary circuit of the transformer. Eastman W.iite Label chemicals were user! I ithout purification. In a tjpicpl experiment 29.L~ grams nf maleic anhydride in 416 ml of cumene were kirculated for two hours in the appmatus while the discharge was mainth'ined at a power level of 400 watts. Nitrogen was suppli?d at the rate o'f'50 al/min. The teqperatiire of the reclction mixture was 127O C. Tne renction mixture iuas ccole.' to 20° C. and the resiilting crystals were filtered and washed with 50 ml of cold benzene. Additional crystals here obtained after the mother liquor had been condensed to one third of its initbal volume by flash evaporation. T!ie combined product was drier! at 50 '-C. in a vacuum oven. It weigned 5.18 grams and had melting point 255-7' C. Elementary analysis and neutralization equivalent were consistent with formula I1 (R = H, R' = i-Pr). The infra-red spectrum showed absence of aromatic cnaracter. Flash evaporation of the unreacted cumene and maleic anhydride left 23.0 grams of a viscous residue which had neutralization equivalent corresponding to a mixture of a 1:l and 2:l adduct of maleic anhydride and cumene. It was assumed that it containLd adduct of formula I (R = R' = Me) together with products of further condensation with maleic anhydride. Infra-red and NMR spectra were consistent with this assumption. Similar results were obtainPd ~laing bencene, toluene, and ethylbenzene as substrates. Chlorobenzene and nitrobenzene failed to yield a crystalline product. "he exwrimental conditions and the results are summarized in table I. Dis cu s s ion. It is apparent from the present results that maleic anhydride forms an adduct of type IT with benzene and alkylbenzenes under the influence of silent discharge. The generally accepted path of formation of IT in photochemical (3) or gamma-radiation induced (10) reaction is % I
- Page 219 and 220: s., Literature Cited Berkley, C. ,
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270<br />
R .ACTION OF 'bI.4LEI.C J.NI?Y?'lRITE WITH ARCFl;\TTC FT'rllRCC.4IIRDNS<br />
UKDER TIi5 INFZUXNCE OF SILENT ZL'XTRIC ?ISC?!.RGX<br />
A.T ATWSPHTRIC F'RZSSVRRE.<br />
Stylianos Sifniades, David Jerolamcn, Robert Fuhrmam'<br />
Allied Chemical Ccrporation, Central Research <strong>Laboratory</strong>, Box 309,<br />
Yorristown, N. 3.<br />
I<br />
Maleic anhydride is lmoyn to form two olasses <strong>of</strong> adducts with<br />
alkyl benzenes, depending on the conditions <strong>of</strong> excitation. A t reflux<br />
. t-peratures and in the presence <strong>of</strong>. catalytic amounts <strong>of</strong> peroxides<br />
adducts <strong>of</strong> type'I 2re formed (1,2). A free radical chain reaction is<br />
assumed involving abstraction <strong>of</strong> a benzylic hydrogen. The chain length,<br />
based on the ratio <strong>of</strong> product to' added peroxide, is 20 to 100.<br />
R<br />
I (R,Rf = II or Me; R"= Me,Et,i-Pr) I1 (R,Rf= H,Me,t-Ru,Cl)<br />
4t FGOIU or somewhat higher temperatures and in the presence <strong>of</strong><br />
ultra-violet radiation aPducts <strong>of</strong> type I1 are formed (3 to 8). Excited<br />
aromatic molecules or excited charge-transfer complexes <strong>of</strong> maleic<br />
anhydride with an aromatic molecule are claimed tc be the reaction<br />
intermediates. The addition is sensitized by benzophenone, but the<br />
adduct can be formed in the absence <strong>of</strong> a sensitizer, although at a<br />
much lower rate. It appears that the presence <strong>of</strong> benzophenone is. iridis-<br />
pensable if sun light is used as the source <strong>of</strong> exciting radiation (9).<br />
It is interesting to note that in this case only benzene forms an<br />
adhct IT with maleic anhydride, while alkylbenzenes are only partly<br />
Incorporated in poly-anhydride chains which are formed.<br />
Recently formation <strong>of</strong> the adduct I1 <strong>of</strong> benzene and maleic anhydride<br />
'under the influence <strong>of</strong> gamma radiation was reported (10). The adduct<br />
is only a minor product ,<strong>of</strong> the reaction, corresponding to about 4% <strong>of</strong><br />
the maleic anhydride spent. The main product is a mixture <strong>of</strong> polyanhydrides.<br />
These can be considered to arise through a free radical<br />
chain similar to the one yielding adducts <strong>of</strong> type I.<br />
It is then clear that in the system maleic anhydride-benzene (6r<br />
alkylbenzene) two types <strong>of</strong> reactions are prevalent, one by free radical<br />
chain yielding adduct T or poly-anhydrides, the other by means <strong>of</strong><br />
excited molecules or charge-transfer complexes yielding adduct II. It<br />
was thought <strong>of</strong> interest to investigate the influence <strong>of</strong> silent or corona<br />
discharge on this system. This type <strong>of</strong> discharge was chosen because it<br />
is easy to maintain at atmospheric pressure.<br />
-iharge apparatus was essentially a modif led Siemens ozonizer<br />
Vertically mounted. It was made <strong>of</strong> Pyrex glass. A solution <strong>of</strong> sodium<br />
chloride in glycerol circulating in the jacket constituted the ground<br />
electrode, while a silver coating In the interior surface <strong>of</strong> the central