Partiallv Fluorinated Esters and Ethers as Temperature=StableLiquids J
P. I). FAUROTE, C. 31. HENDERSON, C. 31. 31URPEI1, J. G. O'REAR, AND H. RAVNER 2Vat.al Research Laboratory, F'ashington 25, D . C .
T
HERE is an increasiiig tlrniand for lubricants and hydraulic
fluids which can meet the severe operational requirements of modern military and industrial equipment. Fluorocarbons, because of their stability, have been suggested for such applications, but their large temperature coefficients of viscosity (32) and high freezing points seriously restrict their utility. Interchain with certain groups-e.g., methylene, rupting the -CF2ester, etc.-decreases hindrance to free rotation and results in compounds n-ith lower freezing points and smaller temperature coefficients of viscosity. T h e properties of such eompounds should be intermediate between those of completely fluorinated and unfluorinated analogs. Filler and coworkers ( I d - 1 6 , 0 2 ) describe some partially fluorinated diesters, most, of which n-ere derived from heptafluorobutyric acid and glycols, or from l H , 1H-heptafluorobutanol-1 and dibasic acids. Recently, fluoroalcohols prepared bj- the telomerization of methanol antl tetrafluoroethylene (3, 2 5 ) , having the general formula H ( C F Y C F ~ ) , , C H ~ Ohave H , become available. Corresponding acids (3) are prepared by oxidation of the alcohols. T h e prescnt st,udy reports a number of cstcrs and some ethers derived from these telonieric acids or alcohols and compares t,heir properties v-ith those derived from fluoroacids or fluoroalcohols containing -CF, terminal groups. Since the official ACS nomenclature of the partially fluorinated acids antl alcohols ( 3 4 ) is long and cumbersome, abbreviated names similar to those used by Grosse and Cady ( 2 0 ) have been adopted. The abbreviations used are as follon-s: ,
ICOOH ,CFI,OH ,CH,OFI
+-arid $-acid +'-alcohol $'-alcohol
n h e r c IL 1s g1eltter thart 1. This nomenclature is extended to the ether and ester del ivatives. Compounds in Tables I and I1 are named by both methods. S Y V T l J E S I S O F CORIPOUNDS
Starting Materials. All starting illaterials (Table I ) n-ere' shown t o he of :tcccptable purity before use. The +'-alcohols were supplicd by E. I . dn Pont de Semours and Co. and were purified by distillation through a 100-plate Podbielniak IIyper-Cd distillation column. As the characterization of these alcohols n-as incomplete (3,pb), assay data are given. T h e $-heptanoic acid was obtained by acidifying its ammonium salt (3). The @-but!-ric antl @-octanoic acids together with the p'-hutyl and p'-hexyl alcohols were obtained from the Minnesota AIining and llanufacturing Co. and were found suitable for use without further purification. +'-Octyl Alcohol. Reduction of 518.0 gritme (1.10 mole) of but>-I6-octanonte Tl-ith 37.9 grams (1.00 mole) of lithiuni aluminum hydride is accomplished bj- conventional procedures (35). Preliminary distillation oi the ether extract from duplicate batches gives 820 grams of crude product (93.27, yield); boiling point, 1-10' t o 164" C . a t 760 nini. of mercury. Redistillation through a 100-plate Podbielniak Hyper-Cal column gives 595.3 grams of +'-octyl alcohol having the properties shon-n in Table I.
445
The boilirig point of 141' t o 112" C ' . :it Tti0 nini. of mercury reported for +'-octyl alcohol ( 1 4 ) is believed t o be in error because of the small amount of alcohol distilled. 1,2,3-Trimethylolpropane. Following the above procedure, 205.3 grams (0.79 niole) of triethJ-l tricarballylate are reduced with 67.0 grams (1.76 moles) of lithium aluminum hydride. The aqueous layer, containing about 80% of the product, is adjusted t o a p H of 9.0 ivith 50y0 aqueous sodium hydroxide. Aluminum hydroside and lithium sulfate precipitate upon the addition of 2 liters of acetone and are removed by filtration. Then the aretone and ether extracts are combined, concentrated, and distilled t o give 136.1 grams of 1,2,3-triniethylolpropane(64.2'% yield); boiling point 160' t o 170" C. at, 0.3 mm. of mercurj'. Two additional distillations through a 12-inrh Vigreus column give 113 grams of viscous, water-white product; boiling point 162" C. a t 0.5 mm. of mercury; n*; 1.4800: d:' 1.111; per cent C (calc.) 53.71, (found) 53.45; per cent H (cnlc.) 10.52, (found) 10.70. Esters. Although good yields of diesters of fluoroalrohola can not be obtained in the presenc-e of acetic anhj-dride (6), direct esterification using p-toluenesulfonir arid is 9atiPfactory (Table 11). Heretofore, the latter procedure hits been considered impracticd ( 1 4 ) . I n general, thc time reqnired for the direct esterification of the fluoroalrohol is comparable Tvitli that required for the reaction of the fluoroalcohol with the acid halide (1.4). Besides giving better J.iclds, the, direct esterification nieiliod eliminates the preparation ;ind piirification of the unstable acid halide intermediate. Crude esters of the fluoroalcohols are diluted n i t h ether, then washed successively u-ith lAY aqueous potassium hydroxide, 0 . 0 1 S hydrochloric acid, and n-ater. Tn-o distillations through a 12-inch 1-igreus column, follon-e(lh;. piarrolations through Florisil and alumina, yield n-ater-n-hitc e s t c ~ s\\-ith neutralization nunihers less than 0.03. T h e second distill:itioii is required t o remove the p-toluenesulfonic acid ester. Esters of fluoroacids are purified 11). t n o distillations through a 12-inrh 1*igreux column at rtdnred pressure and subsequent perco1:ttioris through Florisil and alumina. The final products are water-xhite liquids and odorless, except for those of IOTV molecular weight (Table 11). It is inipossihhie to determine t,he neutralization numbers of these estc>i,s. cis they hydrolyze so rapidly t h a t stable end points can not tic, obtained. +.'-Heptyl Methyl Ether. A charge of 2SO nil. of water, 9.19 grams of sodium hydroxide, and 53.14 gi'aniz (0.16 mole) of $'-heptyl alcohol is stirred while 27.93 grams (0.15 mole) of mrtliyl p-toluenesulfonate are adtled over a 15-minute prriod ( I ? ) . Stirring and refluxing are continiid for 16 hours. Then the Ion-er layer is isolated, diluted with ether, and a.nshed n i t h 6.Y potassicmi liydrosidc. Tn-o distillations give 22.7 gr:cnis (43.77; > icld) of +'-hept\-l methyl ethvr: l ~ i l i i i gpoint 118.5' C. a t 203 nim. of mercury: n z I . : < I N 1,6-Bis($'-heptoxy) Hexane. -1 + d a r 1)rocedure iz used for the reaction of 56.0 gram9 (1.10 mole?) of sodium hj-droxide in 500 nil. of water, 464.9 grams (1.40 moles) of $'-lic,ptyl alcohol and 290.0 grams (0.68 mole) of 1 ,O-he\;:inocliol ~)is(p-toluenes[ilfonate) (36, 3 8 ) ; melting point 71" to 7 2 " C. ( 1 0 ) . Distillation gives 200 grams (%yo yield) of 1 .ti-l,i~;!ii.'-liepto~y)hczane
446
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 48, No. 3
(Loiling point 142" to 14.5' C . at 0.3 nun. of mcrciir:-j tii;rc>ther with 78 grams of 1,2O-his($ '-heptoxy) T:ll-ciio\ac'ir,os:ilie: hoiling point 190' to 203' C. at 0.4 mm. of nierriir:.. .i sccontl distillation followed h y percolation yields procliirts 1i:iviiig the properties shown in Table 111. A N L Y T I C . A L D-IT.4
The boiling points, elernental assaj's, tirid ~vhervapplicaI)le, saponific~ationnumbers of the various fiiioroesters and fluoroethers are summarized in Table 111. In general, there is a direct rehtionship hetn.rrn the rates of saponification and esterification of the fliioroalcohol esters. Saponification of $'-nonyl 2-ethylhelanoate and his( $'-hept!-l) piriatv \vas incomplete, even after 24 hours of reflux, because of shielding of the ester linkages. Boiling Points. Fluoroesters derived from fluoroalcohols arid diba3ic acids are higher boiling than the corresponding esters derived froin glyrols and fluoroarids. I n all instances, diesters prepared from either $'-alcohols or from +acids are higher hoiling than corresponding esters prepared from qi'-alcohols or 0 avida. Density and Refractive Index. Table IV lists densities and refractive indices of the various fluoroestc,ru and fiuoroetht,rs. I n general, density increases iyith increasing fluorine conteiit, but any direct relationship between density and fluorine content is valid only for a given homologous series. Diesters of diha3ic. acids antl fluoronlcohols are more dense than the corresponding isomem derived i'i.oni glycols and fluoroacids. A plot of dciibity 1's. chain length of tlie bis(+'-allcyl) iind his( $'-dkyI) :3-nieth>-lg1utar:ites i,cwilts in :t single sniooth curve, iridimting that thc corresponding esters have comparable densities, although the qi'-aliaohol cstw has the greater fluorine content. Since the his(h'-alkyl) 3-~iictliylglutaratcshave greater molecular weights than do tho corrcspondiiig $ '-analogs, the former have tlie greater free volume in the licliiid state. Cohesive forces could a(l(lount for this plienomenon :is \yell ;is for the higher boiling points of tlie $ ' i,onipountis. Graphical comparison reve:ils that bis($'-alkyl, 3-nicth:,lg1iit:Lr:itm arc> significantly more refractive than the +'-analogs. Trends i n clensity and. refmctive index observed with t h r 3mcthylglutarate esters are the same as those of their parent a k ~ o hols. Tcmper:rture coeffirients of refractivity of the 3-methylg1iit:ir:itr esters \\-ere determined from me:isiirements :it 20", B7.S'! a n d 64" C. Id'or thc his(+'-hutyl, -hc,xyl, antl -oct!-l) :3-11ic~thylgIiita1~:~t~~s values of -I~II;' C. X I O 4 \wrr 3.65, 3.%, and 3.16, respectively, Values of l n w o C. X lo1 for tiis($'aiii:.I, -hrptyl, a r i d -noii>.l) B-nieth!.lglutarates ere 3.1.5, XOO, arid 3.00; ri.spectively. Molecular, Atomic, and Bond Refractions. 1IolecuIar refractions of various fluororonipounds, together with the atomic: :md I)oiid refraction of fluorine, are given in Table I\-. .$tomi(. refractivities vary, depending on the tvpe of c.ompount1 and thc extent of fiuorinc substitution. Surface Tension. The fluorocompourids (Table I-)11:ivr low surface teiwions ( 4 0 )which decrease with the addition of --CFY--groups in a homologous series. Surface tensions of the isomeric 01s arid dibasic. acids are coniparable. Surface tennirthylglutarates tlerivctl from $'-alcohols :we about 5 d?.iic,s pcr cm. highcr than those of the corresponcling +'alcohol derivatives. These dii'ferences are greater than n-ould he expected from thcir fluorine contents. Similar diflerenccs are ohserved betn-een analogous glyrol diesters of $- and +acids. Atomic and Bond Parachors. .itoriiic. and hond parachor? are less sensitive to minor changes in structure than are molccnlar refractionr. 1'arac:horr of fluorine (Table V ) are reasonalile, heing in fair agreement with the value of 25.7 h!- Sugden ( ~ { f ) , 24.6: by Fowler ( 1 8 )and 24.9 - 25.8 by Filler f,1,3'1, V:iliic.s for fluorine derived from L-ogel's constants she\\- Icss variation tlinii thosc derived from Sugden's constants.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 48, No. 3
Table 111. Analytical Data on Partiallj- Fluorinated Esters and Ethers Cvrnpoundj"
Enipirical Formula
Molecular Weight. Theory
Boiling Point, C./hlin Hg
Carbon, ?'?c Calcd. Found
vo
Hydrogen Calcd. Found
Sapoulficatiorl Fluorine, Po _ _ 1-0. Tinien, Calcd. Fourimi Calcd. I F o i l i ~ d HI. ~~
~
Esters Hexyl +butyrate Octaderyi q-butyratec But>-1O-octanoate 1,G-Hexanediol bis(d-butyrate) 1,10-Decanediol bis(+butyrate)
1,G-Ilexanediol bis(+-hepranoate) 1$-Hexanediol bis(+octanoate) 1,2,3-Trimethrlolpropane tris(m-butyrate) $'-Tndecyl acetate &'-Nons1 butyrate &'-~on~-l-2-eth3-Ihexanoatt?
722.27 5i4.18 502,21 j58.31
12010.2 134/20.0 130/20 0 99j0.5
Bis(+'-anij-l) glutarate Bis(@'-butyl) 3-niethj lgliitaiate Bis(+'-am,-l) 3-niethylglutarate Bis($'-hexyl) 3-riiethylglutarate Bis(i'-heptyl) 3-methylglutarate Bis (q'-oct:,.l) 3-niethylglutarate Bis(+'-uonyl) 3-niethylglutarate Bis(i'-aniyl) adipate Bia($'-heptyl) adipate Bis(d'-octyl) adipate
560.25 510.24 574.27 710.28 774 31 910.32 9 i 7 35 574 27 774.31 910 32
134i0.5 8510.5129/0 n 115:o. 5 147i0.5 l4j/0 5 1ei:o. 5 13910 5
Bis($'-nonyl) 3-ter1-butylarlipate Rie(o'-butyl) sebacate
1030 46 5Gfi,34
CisFIiiFziO~ Ci3HsFinOz CiaHioFi60r CirHi~FieOz
Bis(+'-aniyl) cebacate Ais($'-iieptyl) pinate
830.38 614.37
b C
CaHaFnO CzoHioF2aOi
316.13 746.34
C~~HizFz106 946.8F
B3.0 97.7
235 2 97.1
1 4
3 < i 37
3i;.;,s
3.26
3.30
i : i 5
54 JS
3 2 16 ::2 , 9 3 .33 , X i 30 44 d l 02 29.03 29 38 3.3 , 46 31.02 29 03
32.21 32.91 3'3 . 80 30.08 X I . 12 29.22 29.99 33.35 31 10
2 16 2.37
2 46 1.70 1 82 1.33
2 33 2.48
'Y. 14
1.45 2.46 1.82 1 .3:3
2.33 1. fi3 2.12 1.44 1 49 2 48 2.09 1.59
54.26 52 13 52.94 .58.89 fi2.62 62 40 52 94 58.89 6 2 , til
54.05 51.41 52.74 59.04 5%65 62.14 02.29 52 70 58.30 62 I"
100:5 ii.1 64.3 200,3 2 0 0 . 8 219.9 218.9 1 9 5 . 4 194 7 138.0 158.9 144.9 1 4 3 . 2 123.3 125.4 1 1 5 , 2 115.6 195.4 194.5 1 4 4 9 144.f j 1 2 3 . 3 123 4
32 63 38.17
32.85 38 24
2 15 3.56
2.33 3.60
59.00 46.97
.59,0(, 46.80
108.9 198.1
107.2 199.1
24
28.10
33.92
38.23 33.94
3.52 2.23
3 77 2.33
48.23
47.80 55.50
4 4
313.38 30 82
36.43 30.83
1.70 1.73
1.82
5 1 . 1 5 51 37 X , i % 55 46
178 0 1 7 8 . 9 1 3 7 . 8 103 4 129.5 186 8 190.2 2 0 5 . 7 206.0
144/0.5
27 i f 3 32.18
'27 49 81.80
1.7: 2.43
2.78
G5 87 61.10
05 70 00.98
19W0 5
40 60
41.04
4 47
4 85
18 l i
47.72
157/0.5 148/0. u 173/3 ( 1 6 ) 187/0.5 13310.3 130/1 (15) 166/0 5 18510. 5
Bis(+'-amyl) phthalate Tris(+'-amyl) tricarl~allylate Ethers +'-Heptyl niethyl ether l,~j-Bis(i'-IieytoxS-j hexane 1,PO-Bisi +'-heptou>-) 7.14-dioxaeicosane
...
llS,j/203.0
-111 elemental as5aJ-s perfonnrd by Schwarzkopf hlicroanalytical Labs. Reflux in 0 . 1 s alcoholic potassium hydroxide (200% excess:. B.P. a t 4 rnin. Hg reported in hlinnesota Mining and I\Ianufactiiring C o . hrocl!i:i.i, "€Iei,t.irliinrohut\
structure (4,7 ) . This vias the only ester of a fluorinated acid not discolored after its viscosity determination a t 400" F. Viscometric properties of compounds prepared from fluoroalcohols are given in Table VI. One diether, his($'-heptoxy) hexane, is included in this stud?-; all other compounds are esters. T-iscosity-temperature graphs of the fluoroalcohol derivatives curved downn-nrd betn-een 100' and 210" F., as did those of the fluoroacid esters. Like the aliphatic diesters, these partially fluorinated diesters vere difficult t o freeze and it TTas possible to obtain visrosities a t t,emperatures beloiv their freezing points. Most unespectedlj-, the graphs of compounds which were liquid a t subzero tcrnperatures curved dom-nn-ard at, low temperatures. Properties of d i e s t e ~derived from $'-alcohols are shown in Table VIj where they are compared with those of diesters of 6'-alrohols. Esters of $'-alcohols are considerably more viscous than their @'-analogs and have larger viscosity indexes. Increases in viscosity caused by the addition of -CF2or -CH,-groups were of the same magnitude as in the glycol esters of fluorinated acids. T h a t branching increases the viscosity and lowers the viscosit>-index is exemplified by t h e $'-amj.l alcohol esters of glutaric and 3-methylglutaric acids. When a larger branch chain is introduced as in tris( $'-amyl) tricarballylate, these effects are niore pronounced. Two examples of esters with cyclic structures are shown: his( +'-heptyl) pinate Tvith a cyclobutyl ring and bis(4'-amyl) phthalate with a benzenoid ring. Although the pinate ester has the longer chain and higher fluorine content, its viscosity is only slightl>- greater, however its viscosit,!. index is considerably larger than t h a t of the phthalate. Comparison of the viscometric properties of his( $'heptyl) adipate, his(+'-octyl) adipate, and bis(@'-bu$-l) sebacate with those of the isomeric fluoroacid esters reveals that the
1.72 1.81
TIC
58,85
55.99
4
25 4 24
4 ?I 4 4 24 4 4 4 4
24 4
24
.\?id.
latter are less viscous and have larger viscosity indexes (Table
VI). T h e reverse is true for unfluorinated esters ( 4 ) . Comparison of Partially Fluorinated and Unfluorinated Analogs. Properties of some partially fluorinated esters and an ether are compared with those of their unfluorinated counterparts in Table VII. The fluorinated compounds have smaller viscosity indexes and are the more viscous at temperatures of 100" F. and loiver ($3). rit 210' F., three of the fluorinatcd compoiinds-bis(+'-b~it~-l) sebacate, bis(+'-octyl) adipate, anti 1!6-hexanediol his($-octanoate)-have lower viscosities than do their unfluorinated analogs, a manifestation of their larger temperature coefficients of viscosity. Boiling points of the dibasic acid est,ers of fiuoroalcohols bear the same relationship t o each other as do those of the parent alcohols. This relationship also can be used t o predict the relative boiling points of esters derived from fluorinated and unfluorinated alcohols, despite their great differences in molecular veight. L4ttemperatures belo\T 100' F., the diesters of fluoroalcohols are more viscous than their unfluorinated analogs with similar boiling points. Presumably; this would also apply t o derivatives of fluoroacids. Freezing and Pour Points. Freezing points of the variou? fluorinated conigounds are shown in Table TI. Pour point,s arc. reported for the compounds t h a t could not be crystallized. Increasing the chain length of the molecule by adding --CFtgroups raises the freezing point in both the glycol and dihasic arid series of diesters. I n gcneral, diesters n-ith -CF,H terminal groups have Ion-er freezing points than those with -CF, terminal groups. Branch chains lower the freezing point of the partially fluorinated esters a s they do n i t h the aliphatic diesters ( 4 ) . So generalizations relating the freezing points of the partiall?.
March 1956
INDUSTRIAL AND ENGINEERING CHEMISTRY
449
glutaric acid and 4‘- and $‘alcohols. I n both series, the S.I.T.’s are lowered a s the Atomic -CF2-- content is increased. Refraction of Fluorineo Mol. Refraction This is t h e reverse of the Using Using of C-F (MR) Eisnlohr’s Vogel’s effect x i t h glycol esters of fly Compound di0 increments incremente Bondb Obsvd. fluoroacids. Diesteis derived Esters 1.2315 1.3452 1.320 1,225 1.866 51.46 Hexyl +-butprate from 3-methylglutaric acid and 1.4027 1.443 1,938 1.298 107.74 1,0560 Octadecyl +-butyrate $’-alcohols have S.I.T.’s ap1.2246 1.5328 1.180 1.824 $1.65 1,266 Butyl +-octanoate 1.3413 1 4696 1 322 1.229 13.03 1,870 1,6-Hexanediol bis(+-butyrate) prosinlately 50” F. higher 1,236 91.72 1.3588 1,877 1.3594 1.337 1,IO-Decanedicl bis (+butyrate) 1,3474 1.824 1.180 1.272 101 76 l,6-Hexanediol bis ($-heptanoate) 1.6263 than those from +’-alcohols 1.3841 112.65 1.200 1 844 1,6-Hexanediol bis($-octanoate) 1.6687 1,289 with comparable fluorine con1,2,3-Trimethylolpropane tris($-butyr1.3423 1.222 94.44 6137 1 315 1 864 ate) tents. Like the glycol di1.248 5780 1 161 1.803 1,3368 B6.14 &’-Sonyl butyrate 4384 1.3555 1 254 1,159 1 803 84.70 $‘-A-onyl 2-ethi-lhexanoate esters, the s.1.T.’~of dibasic 1.3860 1.229 59sn 1.136 1 . 7 7 9 76.60 Bis($’-amyl) glutarate acid esters decrease as the 1.274 1.3448 1 823 72.36 4968 1.161 Bis($’-but>-l) 3-methylelutarate 5570 1.3595 1.140 1.233 1.783 81.30 Bis( $’-amyl) 3-inethylglutarate chain is increased by the addi1.3386 1 822 1.269 6101 1.li8 92.12 Bis(d‘-hexyl) 3-niethylglutarate 1.3503 101.20 Ris($’-heptyl) 3-methylglutarate 1.249 6484 1,157 1.801 t i o n of -CH2groups. 1.266 6894 1 176 1.3363 1.821 111.83 Bis($’-octyl) 3-methylglutarate S.I.T.’s of the dibasic acid 1.247 1.3452 1. 160 i.801 120.80 Bis(&’-nonyl) 3-methylglutarate ,714 1,3605 5606 1.236 1.141 1.783 Bis(&’-amylj adipate 81.31 esters are higher than those 101.14 1.3510 6516 1.246 1,155 1.803 Bis($’-heptyl) adipate ,6238 139.25 1.3577 1.246 1 797 1.149 Bis (+’-nonyl) 3-tert-butyl adipate of their glycol isomers. 1.3632 3837 Bis(c’-butyl) sebacate 1.290 91.05 1.829 1.188 Mulcahy (28) proposes t n o 4385 1 3740 1.151 Bis($’-amyl) sebacate 1.263 100.08 1.793 Bis($’-heptylj pinate ,6009 1.163 1.806 1.3646 113.56 general niechanisms for hy1 239 6237 1: k33 1.3990 Bis(&‘-amyl) phthalate 1.876 88.53 1,3588 1,148 Tris($’-amyl) tricarballylate 107.18 ,6800 1.790 drocarbon ouidation: a 10% 1.241 Ethers temperature niechanism (be&’-HPr>t>-l methyl ether 6294 1.3164 1.176 1 . mi 1.733 41.71 low ,572” F.), involving per1,3467 1.229 1,128 1,6-Bis~$‘-heptoxy)1,erane ,5776 100.93 1.774 4404 1.290 1,20-Bisi$’-lieptoxy) 7.14-dioxaeicosane 1 40iO 1 105 161 11 1,808 oxide and free radical interCalculated by subtracting required atomic and structural increments of either Eiienlohr ( 1 1 ) or Vogel (46-47) mediates, which depends from observed niolecular refraction. b Calculated by subtracting required bond refractions of Vogel (48)from observed inolecular refraction. markedly on molecular structure; and a high temperat u r e m e c h a n i s m (above 752“ F.)>involving ionic and fluorinated diesters and their unfluonnated analogs could be p ~ ~ o l y t intermediates, ic which depends much less on structure. dran n from the data of Table 1-11. Diesters of fluoroacids have T h e S.I.T.’sof t h e glycol esters of fluoroacids generally fall in loner freezing points than do those of fluoroalcohols I n general, the range of t,he low temperature mechanism, lvhereas those these fl uorinated diesters have relatively high freezing points of the dibasic acid esters of fluoroalcohols are in the high which restrict their lubricant applications. temperature range. Flammabilities. Less flammable oils and h j draulic fluids are It was pointed out above t h a t the S.I.T.’s of glycol esters desired for certain military and commercial applications. I n genincreased as the length of the fluorocarbon chain increased, while eral, flammability resistance can be increased by halogenation those of the dibasic acid esters decreased with lengthening ( $ 2 ) . Hauptschein and con-orkers (22j state t h a t diesters derived from +’-alcohols are nonflammable, b u t no deTable V. .litomic and Bond Parachors of Partially Fluorinated Esters and Ethers tails are reported. Spontasurface Atomic Parachor of Fa parachar Parachor neous ignit’ion temperature Tension. Using Using Of Calcd. Using Dynes/Cm. Eugden’s Vogel s C-F Parachor Av. C--F Bond (S.I.T.j is one measure of flaniCompound a t 20’ C. increments increments Bond b Obsvd. ParsohorsC mahility. T h e apparatus used ( 3 9 ) nnd the experimental conHexyl 6-butvrate 19.2 25.22 23 14 25.61 506. 9 507.7 Octadecyl p-butyrate 25.1 27.21 23 4 1 25.61 988.8 987.7 ditions were the same as in Butyl d-octanoate 18.7 24 42 21 10 24.77 637.9 .... 1,6-Hexanediol his($-butyrate) 21 5 23. 37 23 51 25.77 747 6 previous work ( 4 2 ) . Table 743.9 1,IO-Decanediol his($ -butyrate) 23 0 26.00 23 86 912 4 903.9 26.11 TI11 lists the S.I.T. of each 1,6-Hexanediol bis($-heptanoate) 23.9 25.78 23 86 1074.1 26.07 .... 1,6-Hexanediol bis ($-act a n oa t e ) 24 71 20.6 24.70 22 50 1162.2 .... compound together with its 1.2,3-Trimethg-lolpropanetris(&butyrate) 21.2 24.11 22 31 24.57 960.6 980.2 chain leilath and fluorine con+‘-Sonyl butyrate 22.7 25.08 23.19 25.38 694.7 694 . 9 tent. GIJ-col diesters of fluo+‘-?;any1 2-ethylhexanoate 23.1 25.10 22 96 25.15 850.9 864 9 Bis(&’-amyl) glutarate 2 7 . 5 25.35 23.49 95.73 802 9 797.6 roacids shon- a progressive Bis($’-but~-l)3-methylglutarate 20.6 23.79 21.93 24.18 725.4 .... B/s($’-amyl) 3-methylglutarate 26.8 25.19 23.26 rise in S.I.T. when the chain 25.49 R39.2 837.a Bis(d’-hpxyl) 3-methylglutarate 19 9 23.64 21.77 23.98 931.5 .... length is increased b y adding Bis($’-heptyl) 3-metliylglutarate 25.6 25.05 23.13 25.35 1056 6 1098.0 Rir(o‘-octyl) 3-methylelutarate 19.5 23.72 21.50 23.70 1132 3 .... -CFzgroups. K h e n the Bis(&’-nonyl) 3-nietliylglutarate 25.0 24.89 22.98 25.17 1271 2 1278.4 Bis($’-amyl) adivate 27 7 25.50 22.32 25.80 844.2 f l u o r i n a t e d p o r t i o n of t h e 837.8 Bisf&’-heptyl) adipatc 26.1 23.18 23.26 25.47 1059 7 1058 0 molecule is kept constant and Bis(i’-nonyl) 3-tot-butyl adipate 24.9 24.59 22.56 24.75 1417 6 1138.4 Blsio’-hutyl) schacate 22.4 24.44 22.29 24.54 890 3 .... the chain length increased BE($’ amyl) sebucate 28.2 28.13 23.95 25.56 IOIO 2 997 6 Bie(+’-heptyl) pinate 26.2 25.05 22.95 25.16 1150.9 w i t h -CH2groups, t h e 1156 6 Bis(+’-amyl) phthalate 28.0 24.08 22.63 24.75 852 3 841.9 S.I.T. decreases. Tris($’-aniyl) tricarballylate 27.2 ” 3 00 22 82 25.05 111% 4 1120.7 T h e effect on the S.I.T. of Ethers $‘-Heptyl methyl ether 22.1 24.97 23.15 25.28 460 8 462 1 increasing chain length and 1.6-Bis($’-heptoxy) hexane 23.3 25.72 24.44 25.74 1061.0 1052.8 fluorine content of dibasic Calculated b y subtracting customary increments of Sugden (41)and of Vogel (4:) from the ohserred parachor. b Calculated by subtracting bond parachors of Voeel (48)from the observed parachor. acid esters of fluoroalcohols 6 Average of C--F bond parachor of 25.5 was used for all perfiuorobutyrates and average C-F bond parachor is exemplified by the behavior of 29.4 with all derivatives of +’-alcohols. of the dieEters of 3-methylTable 1V. Atomic and Bond Refraction of Fluorine in Partially Fluorinated Esters and Ethers
~~
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
450 Table VI.
Vol. 48, No. 3
Viscometric and Low Temperature Properties of Compounds from Fluoroacids and Fluoroalcohols Atoms i n Principal Chain, 2
Compound hIonohydric alcohol esters Octadecyl +-butgrate Dihydric alcohol esters 1.6-Hexanediol bis(+butyrate) 1,lO-Decanediol bis(+-butyrate) 1.6-Hexanediol bis(+-heptanoate) 1.6-Hexanediol bisi6-octanoate) Trihydric alcohol esters lI2,3-Trimethylolpropane t ris (+butyrate)
~
400° F
__
2100 I.'
LOOo F.
Viscosity. C s .
O 0 F.
6 8 O F.
-20° F. -40'
F. -65'
F.
H-N -4STSI Slope, Visc. 6&210° F. Index
Freezing Point, 0
€.
From Fluoroacids 23
0.71
2.13
6.99
11.9
....
....
16 20 22 24
0: 5 5 0: 62
1.2% 1.72 3.14 2.37
3 85 5 76 16.8 12.0
6.2a 9.7'' 36a 25.9
32.1 56.8 480n
66 158 ll5Q 291 1,580 5,970
..
15
0.55
2.47
14.5
33"
5GOn
..
....
.,..
0 77
153
54
..
.. ,. ..
0.96 0.85 0.84 0.92
24 129 75 26
- 18 -36 -65b 39
2,010
11,230
..
0.95
926
?,l50
21,000'
0.88
,.
..
665
-41
-0Ob
From Fluoroalcohols
Ethers l,€i-Bis(+'-heptoxy) hexane Monobasic acid esters +'-Nonyl 2-ethylhexanoate
22
Bis +' amyl) adipate Bis{+':heptyl) adipate Bis +' o c t j I) adipate Bis{+'nonyl) 3-terl-butyl adipate ~
0.68
2.59
13.0
28.1
332
16
0.44
1.44
6.18
17 15 17 19 21 23 25 18 22 24 26 20 22 21
0.68 0.41 0.68
2.65 1.25 2.7: 1.9 3 70 2 80 5 25 2.80 3 71 2.73 6.14 1.84 3 59 6 14 4.80
13.7 4.50 15.9 9.1 26.4 18.3 47.4 14.7 23,5 16.0 68 1 6.68 18.6 a9 4 52.6
46.6 .. 130a .. 31.8 56.5 37" 228 12.0 40.1 5,560 177 5 , 60OC 160a
6.74
79.3
24OU
0:so 0 65 0.98 0.73 0.83 0.69 1.10 0.60 0 91
..
0.86 Ris(+'-ainyl) phthalate Tribasic acid esters 1.03 Tris(+'-amyl) tricarballylate 17 a I'alues interpolated or extrapolated. b Pour point. C Determination made on supercooled liquid. d Method not applicable a t this, vigcosity. e Efflux times showed some variations.
12O 29" 8.3& 33" 17. 8a
6fi"
131
36OC
349 63.9 522 235" 1280
8.410
965C 158 1,510 4;270
.. ..
3,200C 21,fiOOC 488C
5 , 3 6 0 40;800
..
19;000°,C
.. ..
..
.. ..
.
..
.. ,.
.. 30,200
,.
..
57
-706
1 .05
d
0
0.88 1.05 0.87 0.96 0.88 0.95 0 84 0 86 0.84 0.92 0.87 0.86 0.79 0.83 0.91
51 26 -60 19 - 41 25 71 57 6 1 112 101 35
- 17 - 35
- 64
-35b 39
0.84
5
-3Ob
-75b 19 -306 61 77
a5
50 99-102 17 36 Ifi
Flash and fire points \%ere determined in a semimicro open fluorocarbon chains. This apparent anomaly may he elplained cup flash point apparatus ( 3 7 ) . Good correlation betn-een flash by the two ignition mechanisms. T h e S.I.T.'s of n-alkanes from and fire points obtained in this cup and in the Cleveland cup is 8 t o 20 carbon atoms vary only slightly (29). Thus, molecular reported ( 3 7 ) ; good correlation is also obtained here. weight is not a n important variable in the low temperature Flash and fire points of the fluorinated esters ranged from oxidation mechanism of these hydrocarbons and, presumably, 300" to 475' F., Table TTII. From these data i t appears t h a t in of glycol diesters. Raising the concentration of the less flammable partially fluorinated esters (fluorine contents of 48 to 62 w i g h t fluorine constituent should increase the ignition temperature of per cent) fluorine coiiiciit is not the variable governing the flash glvcol diesters. In the high temperature mechanism presumed point.. Flash points Lvere plotted against boiling points and a operative in the fluorinated esters of dibasic acids, ignition of linear graph fitted the data n-ell, as did a similar graph for the radicals from pyrolytic breakdown is the dominant reaction. iinfluorinated estei,s. The t,wo graphs were essentially parallel, Since pyrolytic stability decreases with increasing chain length but t h a t for the partially fluorinated esters vias displaced about and molecular Tveight, the ignition temperatures of such esters 35' F. above that for the aliphatic esters. The spread between should decrease as the tluoroalcohol chain is increased. the flash and fire points of the partially fluorinated esters is Contrary to the generalization pertaining to hvdrocarbons t h a t branching raises the S.I.T., the brnuched chain dibasic acid esters of fluorinated alcohols Table VII. Comparison of Properties of Partially Fluorinated and Unfluorinated have l o w r S.I.T.'s than their Compounds normal isomers. The S.I.T. of 1101. R . P . , F. Viscosity. Cs. ASTX H-S Freezing bis( $'-amyl) 3-niethylglutarate wt., a t 0.5 210' 100' 08' Slope Visc. Point, Compound Theory Mm. Hg F. F. F. 08-210' E'. Index F. is aaoroxiiriatelr 100" F. lower 1,6-Ris(+'-heptoxy) hexane 740.3 291 2.59 13.0 28.1 0.88 57 -70b then the S.I.T.'s of its glutarate 46 1.6-Diheptoxy hexane 314.5 309 1.90 5.48 8.8 0.75 173 and d i p a t e analogs. T h e very high S,I,T, of the phthalate 1.6-Hexanediol bis(d-octanoate) 910.3 293 2.37 12.0 2.5.9 0 92 26 39 ester, 1055" F., is a consequence of its stable ring structure. The s . 1 . T . ' ~of his($'-heptyl) pinate and 3-methylglutarate are800 arid 1600 F.higher than
1.6-Hexanediol dioctanoate
751.9
. .,
2.62
8.42
14a
0.70
IF6
~ i ~ ( + ' - a m adipate ~l) Diamyl adipate ( 7 )
574.3 286.4
282 275
2.86 1.72
14.7 4.80
31.8
0.86 0.73
71 131
Bis($'-octyl) adipate Dioctsl adipate
910.3 751.9
298
2.73 2.85
16.0 8.75
37a 14"
0.92 0.65
6 166
Bis(+'-butyl) sehacate Dibutvl sebacate ( L ) B+(+'-heptyl) pinate Diheptyl pinate (2.9)
566 3 314.3 814.4 383 fi
271 302ILOl . . 329 354
1.84 6.63 2.11 6.11 6.14 59.4 3 22 1 2 . 7
12.0 10"
0.86 0.71
112 174
177 23
0.83 0 71
35 161
-35b
