Numerical results on the hypersonic gas flow in viscous interaction regime past sharp circular cones with thermally destructible Teflon surface are presented. Characteristics of the mutual influence between the thermochemical decomposition of the surface and the viscous interaction are revealed

Limanskiy, A. V.

Timoshenko, V. I.

English

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NASA TECHNICAL MEMORANDUM NASA TM-77977
SYNTHESIS OF PYROMELLITIC ACID ESTERS
V. A. Fedorova et al.
NASA-TM-78015 19860012041
Translation of "sintez efirov piromellitovoy kisloty," Visnik
l'vovskogo politekhnicheskogo institut (Journal of the L'vov
Polytechnic Institute), Vol. 139, 1980, pp. 31-33 (ISSN
0460-0436) (UDC 547.585.26)
Source varies: Visnik L'Vivskogo Politekhnicheskogo Institu
JAH!3 19 6
LANGLEYRESEAR3HCENTER
LIBRARY, NASA
H,'_' "-'" _ .'4, VtR_)NIA
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546 DECEMBER 1985
https://ntrs.nasa.gov/search.jsp?R=19860012041 2020-03-20T15:01:27+00:00Z
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_. _i,l.o,dSub,:,l. SYNTHESIS OF PYROMELLITIC ACID _. R.po,,Do,.December 1985
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National Aeronautic and Space Administration ld(. $po.,©,;.iA_.ncy Co_.
Washington, DC 20546
15.s_pp'l....,©,yHo,,, Translation of "sintez efirov piromellitovoy kisloty,"
Visnik l'vovskogo politekhnicheskogo institut (Journal of the L'vov Polytechnic
Institute), Vol. 139, 1980, pp. 31-33 (ISSN 0460-0436) (UDC 547.585.26).
I_.A_,,,oc,This article studies the ester acids necessary for studying the thermo-
chemica! properties,of pyrome!litic acid (PMK)-based peroxides. It covers
obtaining a tetrameth_l ester of a PMK. The mechanism of an esterification
reaction is discussed, as is the complete.ester!fication of PMK with primary
alcohol.
-°
_- 17. Key W©,_s (selectedby Author(s)) 18. D;,,,;but;enS,et*m*nt
."-" " Uh_imited
19. S,€,.,,ily Cle,s;f. (el Ih|, ,,_o,t) 20. S.cv,,ily Cl.,,If. (el Ihl, f"l') I 21. H,. -f Pel-" I 22. P,ic,,"-'"
Unclassified Unclassified i 6 1 '
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SYNTHESIS OF PYROMELLITIC ACID ESTERS
V. A. Fedorova, V. A. Donchak, A. N. Martynyuk-Lototskaya
When studying the thermochemical properties of pyro- /31.
mellitic acid (PMK)-based peroxides, it was necessary to obtain
complete and n-alkyl ester acids for this acid.
A tetramethyl ester of a PMK is obtained by acylation of
alcohols PMK in an air-fluidized bed in the presence of special
catalysts [2], in a liquid phase--in the presence of a
concentrated sulphuric acid [i] during the interaction of
pyromellitic dianhydride (PMDA) with dimethyl sulphite at
II0-120°C [3].
The mechanism of an esterification reaction, as it is known,
corresponds to the following arrangement: primary protonization
of a carboxylic acid for the formation of active particles of
electrophilic nature which combines the nucleophilic alcohol with
the formation of a secondary oxonium ion. This induces the
migration of a proton from alkylated oxygen to hydroxyl with the
splitting of a water molecule and the formation of a complex
ester. The reactivity of anhydrides is higher than that of
carboxylic acids; therefore, the reaction of esterification
proceeds with a quantitative yield without the protonization of
an anhydride, usually in an excess of alcohol. According to
acylating activities, even the acetic anhydride exceeds PMDA.
Therefore, the acids of methyl and ether esters were obtained by
acylation of suitable alcohols for PMK in a multiple excess of
alcohol (usually 20 moles of alcohol for one mole of PMDA) for
homogenizing the reaction medium and for completeness of the
*Numbers in the margin indicate pagination in the foreign text.
3
acylation reaction at the boiling temperature of a reaction
mass. I and I, with a yield of 97.8 and 96.7_, respectively, are
obtained by using these methods. The acylation reaction rate of
n-propyl alcohol is noticeably decreased as a result of the
decrease of its nucleophile; therefore, there is a difference in
the activity of two reaction centers of PMDA in relation to
n-propyl alcohol. For this reason, after an hour's contact with
the reagents, a product of half-esterification of IIIa (80_) is
obtained and only 20_ of an acidic di-n-propyl ester of PMK (III)
is as follows
Further esterification of IIIa was reached by an addition to /32
the reaction mass of catalytic quantities of pyridine.
Complete esterification of PMK with primary alcohol prior to
the tetraalkyl esters occurs when the reagents are dissolved in
concentrated sulphuric acid. The mechanism of this reaction
includes two stages: the formation of acids of dialkyl esters of
PMK and then the protonization of carboxyl groups which appeared
with a nucleophilic substitution for alkoxy groups according to
the arrangement
... . .-....- ./- -.:.." ._ -
- : - .- . .- .. -.. . , =_ .-: .. : ..
I i
....OC. __ to- #o_ ",OLL _,. _ t'_o_ ,_R ;_r_"r cc._R _.°• o .1()1 o .... .-o .. --
• . . lk.J}
.....-. "OC_ CO" _ ".- - "OC"k,_ rOOH - , _oo,,_f "cooH
• _ . . o . _.
" ' "Ro_c.._ co_ __o._ . _'ooc cco'R
h'O"C. ,_'U,, -2_0 _qOOg"v COORI _ * "2H*0 0 " " ... "'.
4
In proportion to the increase of a hydrocarbon radical, a
steric hindrance occurs in the alcohol, the reaction rate is
reduced, and the product yield is decreased. Thus, IV is
obtained by this method with a yield of (97.2_), V--94.4_, and
VI--91.7_.
Products I--III are crystallized out by diluting the reaction
mass with a 5_ solution of HC1. These products (I-III) were
purified by recrystallizations from suitable water alcohols and
then dried in a vacuum. Tetraalkyl pyromellitic IV-VI were
crystallized out when the reaction mass was diluted with ten
units of cold water. The precipitated crystals were filtered out
and purified by the recrystallizations of water alcohols.
Synthesized esters were identified by the boiling temperature or
by the melting and element analysis (see table).
Characteristics of di- and tetraelkyl pyromellitic esters
1 tlon / t_e. [_, z IK.oh..* i I-eTx [K.oh.*
Ester, T'.C time.¥ield,(Boiling[hoursZ ! teCP'): - Img XOH/g Formula. rngKOH/g.a , , - .-" •
Dimethylpyro- 66 0,5 97 8 297 51,0_ _98,0 CaH_Os 5[,07997.6
mellitic (I) " " ' / i
...°
Diethyl pyro- 80 0.5 -u6,7 219 5t,,22 361,2 _n./_ 5%I9 361.6
mellitic (II)
Dipropyl pyro- ._ 0,5 92,_ I_2 56,71 993,7 C_M_.0$56,_933%1
lellitic (III)
i"
Tetramethyl pyro- IC_ 2.0 _,2 I_I 5_,Z2 C.r,.Ol _ '_
mellitic (IV)
.#
122 2,0 9_,_ 56 5S,9_ - _._.,,%J-(59'0!-Tetraethyl pyro-
,,ellitic (V) " '
a
E2,53 '
Tetrepropyl pyro- - -
mellitic (V) 150 2,0 91,7(242j/.0,65 C. Ms_Oj 62_53
millimeters of
mercury column)
*Translator's note: K. ch. may be Curie unit.
It is apparent from the table that by increasing the /33
hydrocarbon radical of an alkoxyl component, a decrease in the
melting temperature associated with the increase in the volume of
a molecule takes place. Acid esters have a higher melting
temperature and are more easily crystallized than tetraalkyl
pyromellitic esters.
5
REFERENCES
i. Nazarov, N. N., Samenovskiy, A. V. "Khlormetilirovania
toluola" [Chloromethylation of Toluene], Proceedings from the
Academy of Science of the U.S.S.R., Department of Chemical
Sciences, 1956, No. 12, pp. 1487-1492.
2. Benning I., Novotny R., Patent 37630 (German Democratic
Republic), "Sposob polucheniya efirov karbonovykh kislot" [A
Method for Obtaining Esters of Carboxylic Acid], published
07/06/65.
3. Patent 104299 (Holland), "Sposob polycheniya slozhnykh efirov
vzaimodeystviem angidridov so spirtami v prisutstvii
sernistoy kisloty" [A Method for Obtaining Complex Esters by
the Interaction of Anhydrides with Alcohols in the Presence
of Sulphurous Acid], published 04/06/63.
The article was received by the editorial staff on May 16, 1979.
6
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3 1176 00188 9675


Mutual effect of thermochemical surface decomposition and viscous interaction during hypersonic flow past a sharp cone

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