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Issue Date 1956-02-20 URL http://hdl.handle.

1 Ttle The reacton between urea and phtha pressure Author(s) Yanagmoto, Takao Ctaton The Revew of Physcal Chemstry of 77 Issue Date URL Rght Type Departmental Bulletn Paper Textverson publsher Kyoto Unversty

2 THE REACTION BETWEEN UREA AND PHTHALIC ANHYDRIDE UNDER PRESSURE BY TA%AO YANAGIMOTO Introduckon The pressure effects on varous chemcal reactons have been studed'^i up to a pressure of about 15,OOOkg/cm by the author and hs coworkers these several years. It s known that the pressure effect on a chemcal reacton s caused by the dfference, OV, of molecular volume between the reactants and the reacton products. It s expected that the condensaton s accelerated by applyng pressure because the reacton products have smaller volume than the reactants, that s, OV }tas negatve value. In ths paper the condensaton of phthalc anhydrde and urea s expermented as an example. Under the ordnary pressure, t s already knowns 61 that by heatng the tnxed sample contanng equmolecular quanttes of phthalc anhydrde and urea at `C the addtve reacton s carred out and the acyclc urede of phthalc acd s produced. OCOO ~ O + NH.CONH: ~ UCOOHCONH: The pressure effects on ths reacton are studed up to a pressure of 7,OOOkg/cros and a temperature of 136`C. Expermentals Sampler Urea : t s recrystallzed from an aqueous soluton of commercal urea and s used as 150 mesh fne powder. Phthalc anhydrde: t s purfed by sublmatng crude phthalc anhydrde and s used as 150 mesh fne powder. chlorde. Both samples are dred up and allowed to reman n the desccator wth calcum Apparatus and procedure Under the ordnary and hgh pressure, the exper mental apparatus and the method of applyng pressure were the same as the reportsr ^1 of ths Journal. The mxed sample s made by mxng the dred urea wth the dred phthalc anhydrde n an agate mortar at equmolecular or other defnte rato and t 1) R. Kyama sad T. Yanagmo[o, Ths Jarrrna7, 21, 32, 41, 44 (1951) 2) R Kyama and T, Yanagmoto, bd., 22, 34, 39 (1952) 3) T. Yanagmoto, bd., 23, 54 (1953) 4) T. Yanagmoto, bd., 24, 1 (1954) 5) A. Putt, Ann., 214, 17 (1882) 6) C. S. Smth, and C. J. Cavallto, J. Am. Chem. Soc., 81, 2218 (1939)

3 72 T. Yanagmoto s heated for a desred tme under a desred pressure n the form of powder or of pellet made by compressng the mxed. powder to a defnte pressure. Analytcal method The separaton of the reacton product s carred out accordng to the methodsl of A. Pttt as follows. The reacted sample s washed wth cold water of a defnte quantty, as the urede of phthalc acd s seldom dssolved wth cold water, n order to take away the unreacted one, dred up n the thermostat at 70 C. Then, the dred sample s washed wth ether to remove the by-procuct phthalmde and the resdual reacton product, the urede, s recrystallzed from the hot water. After the recrystallzed urede was dred up to a constant weght n the thermostat at 100`C, ts weght s measured. Resulks At room temperature At room temperature, though the followng condtons are subjected to the mxed sample of area wth phthalc anhydrde, the formaton of the urede of phthalc acd does not be detected: 1) keepng the mxed sample n the desccator for a month under ordnary pressure, 2) rubbng strongly both samples n an agate mortar, 3) applyng the pressure of 7,000kg/cm' to the mxed sample for three hours. At elevated temperature 1) The mxed samples of equmolecular quantty are heated n the sealed glass tube by use of the ol bath at a defnte temperature n the range of 80^-136 C. These results aze shown n Fg. 1. When the mxed sample s heated at 80 C, t does not melt and the formaton of the urede of phthalc acd can en use IaC Y 2~ II6C ~~ 45'C [ mc 3D by 90 lal W 18D Tme, mnmes Fg. 1. The relatons between yeld. of the urede and tme at the ocdnary pressure not be detected. At 95 ~ 116 C the temperature of the reactants rses slowly for a tme hgher than that of ol bath, and t s observed that the reactant melts paztally and the urede s formed When above 126 C the temperature rses quckly, the sold sample s wholly changed to the lqud state and the formaton of the urede ncreases rapdly, but, as tme goes on, the temperature of the reactants falls slowly to that of the ol bath, the urede of hgher meltng pont forms, and consequently the reactants are soldfed to a hard mass. Besdes, heatng the reactants for a long tme above

4 t The Reacton between Urea and Yhthalc Anbydrde under Pressure 'C, t s observed that the pressures of the reactants n the sealed glass tubes ncrease, and the hexagonal crystals of phthalmde produced by the decomposton of the urede are deposted from the washed ether. 2) By compressng the mred powder of equmolecular quantty of urea and phthalc anhydrde to the varous desred pressures at room temperature the pellet s made and then t s heated n a sealed glass tube for desred hours. Thes_ results are shown n Fg. 2. In the case of heatng the pellet at lof'c for 30 or 60 mnutes, t s melted partally and the yeld of the urede ncreas s wth elevatng the pressure whch makes the pellet, but over 3,000kg/cm the rates of ncrease become small. In the case of heatng the pellets at 116 C, the whole samples are changed to the lqud state temporarly wth ncreasng the temperature wthn about 15. mnutes n spte of the magntudes of pressure makng the pellets, but n 20 mnutes t s almost soldfed. That s, all the pellets, n comparson wth the powder sample, are entrely melted temporarly at lower temperature and have twce yelds, but the dfference by the magntudes of the pressure makng pellets could not be found on the yeld ~~ 3 a' 30 ~a 2 d V_ ,OOD Prcnurc. kgrcm' m so ~ >~ Fg. 2 The relatons between yeld of the Tme, mnutes urede and pressures makng the pellets Fg. 3 The relatons between yeld of the 1: 106 C, 60 mnutes heatng urede and tme at 126 C 2: 106 C, 30 mnutes heatng 1: lkg/cm= 2: 1,000 kg/cros 3: 116 C, 1~ mnutes heatng 3: 2,000kg/cm= 4: 3,000 kg/cm= 3) Aftet the mxed powder of equmolecular quantty was heated up to about 80-C n a pressure-proof vessel, t s compressed to a desred pressure and heated to 95,-136 C wthn about 10 mnutes, but the formaton of the urede. s not detected n course of ths operaton. When the mxed samples heated for 2 hours at 95 C or 116'C under the ordnary pressure the yelds of the urede are 11 ~ or 39 e respectvely, but under the ext=_rnal pressure of 1,000kg/cme xt 9~ C or $OOOkg/cm= at 116 C for the same hours, the urede s not detected. Under the external pressure of 1,000kg/cm', n place of the above mentoned 2,000kg/cm=, at 116 C for 2 hours the yeld of the

5 74 T. Yanagmoto urede s only a trace. The results obtaned by the experments of 126 C and 136 C under external pressures are shownn Fgs. 3 and 4. In the ntal stage of the reacton the rates are retarded by theexternal pressure and at a defnte temperature the hgher the pressure becomes the longer the nducton perod, but, cvth the rse of temperature the nducton perod on varous pressures becomes shorter and almost the equal, and moreover the pressure effect decreases- After the nducton perod fnshed, t s observed that the reacton rates are accelerated and the yelds of the reacton products ncrease wth ncreasng pressure. Moreover, n the experments of the above 126`C under the ordnary pressure the formaton of phthalmde s observed, but under hgh pressure t s not observed t 3n 4 ~'~ ~ x ~!" ~ ~a IQ Tme. mnutes FIg. 4 The relatons between yeld of the urede and tme at 136 C as ~ Tme, mnutes Fg. 5 The nducton perod n varous mole ratos at 126 C, 2,000kg/cm"- 1; lkg/cm= 2: 1,OpOkg/cm= mole [ato 3: 2,000 kg/cm' 4: 3,000kg/cm= crave 1 earea 1 yhthalc anhyd>de /2 For the purpose of observng the changes of the nducton perod by changng the mole ratos of urea and phthalc anhydrde, ths reacton n varous mole ratos s carred out at 126 C under 2,OOOkg/cm=. These results are shown n Fg. 5. When the mole ratos of urea and phthalc anhydrde are changed as 1:1, 1:2 and 1:4, t s known that the nducton perods become shorter at 30, 20 and 15 mnutes respectvely- On the other hand, when the quantty of phthalc anhydrde s decreased to 1/2 mole aganst 1 mole of urea, the nducton perod s not changed, but the yeld ncreases to some extent. Consderatons Numerous reactons of the sold state n norganc substances aze studed and

The Reacton between Urea and Phthalc Anhydrde under Pressure 75 reported n several papersr s~sl, but the reacton n organc substances s scarcely studed.

6 The Reacton between Urea and Phthalc Anhydrde under Pressure 75 reported n several papersr s~sl, but the reacton n organc substances s scarcely studed. It s knowns> that the reactons of the sold state n norganc substances are commenced exothermcally at the temperature lower than the meltng pont of that substance and aze nfluenced a pror by some factors as temperature, pressure, prepazaton of sample, thermal hstory, mpurty, sze of powder partcle, homogenety of mxture, etc. In ths experment the nfluences of pressure and temperature are manly studed, the other condtons beng fxed as hard as possble. 1) From the results at room temperature, the reacton product could not b obtaned by ncreasng the contact surface only due to the compresson of the mxed sample or rubbng of both samples n the mxng. 2) It s known from the results on hgh temperatures under the ordnary pressure that ths reacton takes place at the temperature between 80-~95 C. In the sold reacton Tamman had proposeds s 10> the relatons between the absolute temperature T~ K (Tamman temperature) at whch the reacton takes place and the absolute meltng pont T.u K, or the rato of To/Tu s approxmately 0.3 for metals, 0.5 for norganc substances and 0.9 for organc compounds. As the meltng ponts of urea and phthalc anhydrde aze 133 C and 131`C respectvely, ths expermental result that the reacton takes place at about 90 C concdes wth Tamman's proposton. It s observed by heatng the powder-mxed sample under the ordnary pressure as follows ; t does not melt at 80 C, but melts partally at 95 ~ 116`C and wholly above 126`C. It has been knowns> on the sold reactons that, wth the rse of temperature of the system by the heat of reacton evolved when the reacton has begun to occur, there s the case where a lqud phase s formed. For example, a-phenyl-r-methylallyl hydrogen phthalate was observed to be transformed by heatng n the sold state nto 7-phenyl-a-methylallyl hydrogen phthalate whch had a hgher meltng pont, and t was knownt~> that the melted state appeazed as the ntermedate stage. In the smlar manner, t s consdered to pass the process of melted state n ths reacton. That s, n the contact surfaces of the two reactants the exothermc reacton proceeds and thereby the sampte melts non-sothermally once wth the rse of temperature n the system. But, t s consdered that, as tme goes on, the urede s produced and here wth the temp~sature of the reacton system falls to that of the thermostat wth the retardaton of the reacton rate snce the contact between both reactants s ntercepted by the formed urede and, for these reasons, the reacton system s soldfed. It has been knowns> that the urede of phthalc acd was decomposed by heatng over about 150`C and phthalmde was formed. 7) J. R. Partngton, An Aduoaced Treates on Physcal Chemstry, 3, p. 5 (1952) 8) A. L, G. Rees, Chemstry of the DeJat Sold Stale, p. 81, 90 (1954) 9) G. Cohn, Chem. Reu., 42, 527 (1948) 10) G. Tamman and Q. A. Mansur, Z. onorg. Clrem 126, 119 (1923) 11) J. Kenyon and S. M. Yartrldge. J. Clcem. Sx., 207 (1937)

76 T. Yanagmolo GCOOHCONH_ ~ ~ ~ + NH, + CO: In ths experment, t seems reasonable to consder that, heatng the mxed sample above 126 C for a long tme, the gas pressure n the glass vessel ncreases and

7 76 T. Yanagmolo GCOOHCONH_ ~ ~ ~ + NH, + CO: In ths experment, t seems reasonable to consder that, heatng the mxed sample above 126 C for a long tme, the gas pressure n the glass vessel ncreases and phthalmde s detected, s due to ths decomposton. 3) It has been known n the case of heatng the pellets, whch are formed by compressng the mxed sample at ordnary temperature, at 106 C ~ 116 C under the ordnary pressure, that the reacton rate has the lazger than that n the case of nonpellet form., In the smlar manner, by usng the pellets made by compresson as the sample, the on exchange reactons72l of PbCrO,-PbCl, and addtve reactons13> of Fe_Os -:- MO---~Fe:O, MO (M= N, Mg, Pb) has been studed under the ocdnazy pressure and n both cases t s known that the larger the magntude of compresson becomes, the larger the reacton rate s because of the ncrease of the contact surface. But, t s observed from the experments at 1D6 C that the rato of ncreasng of yeld aganst that of compresson at over 3,000 kg/cm= becomes small. As known from the experments of e]ectrc resstance under hgh pressures oa slver bromde by Kolttloff141, potassum ferrocyande by the authors=~ and rochelle salt by Okamoto~s> the powder may become almost the compact one by applyng the pressure of 1,50(1-3,000 kg/cm'. Therefore, t seems reasonable to assume that the above fact s due to the decrease of the ncrement of the contact surfaces between the reactng partcles even f the compresson s over that pressure. In the case of heatng the mxed sample at 116`C, though the powder sample s partally melted, the pellets are wholly melted once wthn about 15 mnutes n order to accelerate the reacton rate by the larger contact surfaces. Therefore, the pellets have about twce yelds as compared wth the powder sample, but t seems that the dfference of the yeld by the magntude of pressures makng the pellets s not observed n order to pass the lqud state n the course of the reacton. 4) Under the pressure of 1,000-V 3,000kg/tnt, when the mxed samples are heated for a defnte tme n the pressure-proof vessel at the temperature range of 95 ^- 136 C, t Is known that the ntal state of the reacton has nducton perod, but, rsng the temperature ths nducton perod becomes short and the pressure effect on the nduc ton perod dmnshed. On the other hand, t s consdered that under the ordnary pressure ths reacton proceeds by way of the melted state. Then, t mght be consdered that the appearance of the nducton perod under pressure s caused by the lapse of the tme for the melted state to occur. As ths reacton s exothermc, t seems most reasonable to assume that, accumulatng the more reacton heat over than 12) E. Gled[sch, Bull. Soc. Chm. Frm~ee, 16 D, 59 (1949) 13) H. Forester, Ch. Haasser and 7. Esrard Longuet, bd., 16 D, 146 (1949) 14) L Sphapro and I. Bf. Koltho[f, J. Phys. Collod Chem., 52, 1319 (1948) 15) T. Yanagmoto, Ths Joun~nl, 23, 30 (1953) 16) F. Okamoto, bd., 24, 9 (1954)

8 The Reacton he[ween Urea and Phthalc Anhydrde under Pressure 77 the loss from the reacton system due to conducton, the reacton system self-heats non-sothermally and after a whle the melted state appeazs suddenly. On the other hand, as the meltng pont of the mxed sample s rasedtn under hgh pressures, t s expected that wth elevatng the external pressure the sample s less melted. Therefore, t s consdered that the hgher the pressure s appled and the lower the temperature to heat s, the longer the nducton perod becomes. After the nducton perod fmshed, as the reacton system becomes the lqud state, the pressure effect based on the dfference of molecular volume, ~1V, between the reactants and reacton products becomes effectve4 te>. That s, ncreasng the pressure the reacton rate and the yeld ncrease. It may be assumed that, as ths reacton s the condensaton of one molecule formaton from two molecules, the decrease of rtoleculaz volume s expected n general and besdes ths reacton s an exothermc one and the formaton of phthalmde obtaned by decomposton of the urede s retarded by the external pressure. The mxed sample of the excess of phthalc anhydrde aganst urea has the shorter nducton perod than that of the equmolecular quantty or has good yeld for the same reacton tme. Because phthalc anhydrde has a lower meltng pont than urea and s easly dspersed by heatng, t seems most reasonable to assume that, ncreasng the excess amount of phthalc anhydrde, t gel s near the powder partcle of urea more closely, the contact surfaces ncrease and consequently the ntal state of the reacton s accelerated. The author has great pleasure n expressng hs hearty thanks to Professor R. Kyama for hs advce and encouragement throughout the course of ths nvestgaton. He s also ndebted to the Department of Educaton for the Grant n. Ad to the Researches by Junor Reseazchers n Research Insttutons. The Laboratory of Physcal Chemstry, Ifyoto Unversty 17) P. W. Brdgman, The Physcs of Hglt Pressure, p. 199 (1999) 18) M. G. Evans and 11I. Polany. Trans. Farad. Soc., 31, 875 (1935); 32, 133 (1936)

TitleSynthesis of melamine from urea, II.

TitleSynthesis of melamine from urea, II. TtleSynthess of melamne from urea, II Author(s) Knoshta, Hdeo Ctaton The Revew of Physcal Chemstry of 7 Issue Date 9-0- URL http://hdl.handle.net//7 Rght Type Departmental Bulletn Paper Textverson publsher