Titration of Bases in Dioxane J4\1ES S. F R I T Z llryne 1 ’ n i w r s i t y , D e t r o i t 1 , Mich. The titration of Fariotis organic bases in dioxane with a dioxane solution of perchloric acid is described. Modified niethj1 orange and methjl red are satisfactor) indicators. Most nitrogen heteroc: clic bases and aliphatic amines may he accurately titrated; aromatic amines are too weak to he titrated. Water and alcohol interfere if present i i i milch more than trace amount*. ’
A S Y organic bases cannot be titrated directly in aqutwus solut,ion because they are either too weak to give a sharp end point or only slightly soluble in watrr. For these reasons the use of nonaqucous solvents has been advocated. Various alcohols and alcohol mistures have been suggested (4, 6, 8, 11). A disad-
‘I’uble 11. Sol\.cnt
vantage in thr use of alcohol is that most bases are weaker in alcohol than in water. Palit (IO)titrated salts of weak acids and several nitrogcn bases in various glycol mistures to either a potentiometric. 01’ visual end point,. Aniline was accurately titrated, , were obtainrd in the titration of pyridine hut ve1.y ~ O O I results and rr.lated compounds. Other solvents whirh have been used for t,he titration of bases arc acetic acid ( I , 3,.9), formic acid ( 6 ) ,and benzene ( 7 ) . Diosane ~csrv(’sas an escellent solvelit for the titration of most organic bases. Thc titrating acid is a solution of perchloric acid in dioxane which may be kept for sevwal weeks with little changts in t i t w . 1Iodified methyl orange (sylcnccyanol) or methyl red serv(3s as indicator, giving sharp cnd points. The titration of most 1)asc.a may thus lw quivkly arid cmnvcnic~ntlyrarried oiit, .vI‘I‘Ro(:I.:\
I I I . ~ : K O C Y C L I ( :H 4 s
\\‘I,
t1.r
Titration of Benzylamine with Perchloric tcitl in Dioxanc and Water
\vt.
lICl04 Csed
0.207:
1!).48 21 .RB
Taken
0.2330
HClOa !18.31 !l8.11
0.0977
AI..
w
Pyridine (K?,= 1.4 X although too weak to bcs titi,atrtl accui,ately in water, can be easily determined by titration i i i dioxane to the modified methyl orange end point. During th(8 titration, pyridine perchlorate comes down as a slightly solubl(~ white precipitate. This precipitate in no way interferes with thv end point-in fact, i t is chiefly responsible for the sharpness of the end point because the pyridiniuni ion is thus effectively removed from solution. 2,2’-Hipyritliiie and I , 10-~~lic~i:tritliroli11c may be titratcd as
98.21
iiiiiiioari~lbases in diosaiic- t I) t l i i , iiiotlified methyl orange c ~ i i c l I)oirit oi’ in ethyl ether t o thc, nwthyl wd end point. The perchloi.:ttcb salt of‘ these bast.. pt~wipitatos (luring the titration. Brucines ( K l = 9 X K , = 2 X 10 - 1 2 ) i. insufficiently soluble i n \vatvr to bc titrated dirwtly. but in dioxane may be conveniently iitratcd as a monoacid tmw. 131,11cinemonoperchlomtc, is p r ~ cipitated. 2,B-Lutidine givcs an c~tremelysharp end point \$it11 iiiodified methyl orange; an emulsion is formed during thr titixtion. Hexamethylenetetramine ( K b = 8 X 10-1”) can also htr sucwssfully titrated in diosane n-ith modified methyl orange ititlicator. It is usually difficult to get hexaniethylenet,etraniinc c*onipletely in solution without using excessive amounts of dios:mv. However, if the titration is carried out slowly with efficient stii~ing,accurate results are obtained even if solution of the origitial sample !vas not complctc. Quantitative results for the' ahovc titrations are givoli in TaMP I. 4\II‘iES
‘l’a1)Ic~ I.
Thc titration of anilinc i n tlioxane was attempted, but, botli
Titration of Ileteroqclic Hases with I’rrcliloric~ Acid i n Dioxane
t l i c modified methyl orange anti methyl red end points are very
poor. S o precipitate appears during the titration. Aliphatic. aniinr,s can be successfu1l~-titrated in dioxane, even though thr pcsrchlorate salt of the amine does not precipitate. As an esanipl(i, benzylamine \vas tit rated in both dioxane and ethyl ethrr wing modified methyl orang(. and methyl red, respectively, as indicators. The results ot)taincd by this titration agree with those obtained by titrating I~c~nz~laiiiine in water with aqueous ~ ~ c ~ ~ ~ carid ~ h l o(Tablc ~ ~ i c 11). .
I3a.c.
Pyridint,
0.1987 0.1183 0.2373 0,1622
21.87 18.64 29.70 20.30
0.217!1 0.2613
20.00 23.08
0.09!12
0.210.5 0,3000 0.3167 0.3173
13.63 19.13 20.50
0 0988
0.3596 0.4168 0.3700
18.20 21.03 18.70
0.09!)4
0.1700 0.7590 0.7486
12.20 1!J 72 19.17
0.0976
98.39 98.81 98.30 98.3!)
A\..
.iv.
20.69
IA’I‘ERFISHENCES
\\atvr and alcohols interfere with all of the previously tlvrrribc>d titrations. The indirator blank with both modified nwthyl orange and methyl red in 90% dioxane-lO% \vatel., for (,sample, amounts to several milliliters of 0.1 N perchloric acid. Thc conversion of these indicators to their acid colors is very gradual. Alcohols interfere in a similar manner to water, but not to such a great extent. Ketones, aldehydes, hydrocarbons, nitrobenzene, and most carboxylic acids d o not interfere. I n Table 111, the results obtained by titrating hesameth~1rnetc~tr~~niinc~i n the presence of variou~impurities are g i v m .
99.94 !3!1, 67
XI , 30 99 , .5.3
Ar; Brrioinc
!17.38
100.01 99 89 99.83 100.02
A\.. 1.10-I’liciiaiitl~roline
08.80
! ) 7 ..78 !J7.J7
O ! ) .J l 00 88 99 , !I7 100.07
578
V O L U M E 22, NO. 4, A P R I L 1 9 5 0
579
‘I’able 111. Titration of llexanicthylenetetraiiiinei n Presence of 0.5 to 1 (;rum of .4dded Impurities l\’t.
T i c Lon
I in1111 rit J
0.
O.”ilG 0.3271 0,2464 0.2771 0 . “(i2
None C H C O C H t C I i s)! None tert-Butyl ulcolml h-itrobt:narii,~
I IC104 Csed .111. 19.93
24,OO 18.03 20.60 2i.oi
s
Purity %
0.0972 0.0979 0.0972 0.0972 0.0972
!&I, ‘30 99.98 99.82 100,80 ion.03
HClOi
Thc~ionization of most acids and bases dissolved in diosane and other solvents with low dielectric constants is very slight. (An exception u-odd br solvents’ possessing pronounced acid or basic properties. The ionization of acids in pyridine, for example, would be comparatively gwat.) In such media, an acid-base titration involving ions would, therefore, be expected to proceed i n a sluggish fashion t o give a very poor end point. All the haws that have becii titrated successfully in diosane, however, are ric~utraland do not react as ion?;. A strong acid, H-4, will react wadily with such :t r i c ~ \ i t r , : ~hl t q e
CT>,S + ll.\
I’ltoi-‘I I ~ ~ r i n i a standard. ry
I l E ~ ~ ~Octo1,er ~ I v ~ 14. : ~ l!l4!),
Separation and Analysis of Polynuclear Compounds by Countercurrent Distribution CALYlN GOLUllIBlC tlrireciic. of Mines, O f i c e of Synthetic Liyrcid Ftcels,
I j r i t w f o n , Pit.
T h e partition coefficients of eighteen polynuclear compounds ha\e been deterniined i n the system, cyclohexane-80% ethyl alcohol. Partial saturation of ring structures and introduction of alkyl side chains increase the partition coefficients of parent compounds. Ring systems containing hetero nitrogen and oxygen atonis ha\ e appreciably lower partition coefficients than corresponding carbocyclic structures. These effects permit application oE the countercurrent distribution method to separation arid analysis of polynuclear compounds. The countercurrent distributions of phenanthrene, acenaphthene, ani1 a niixture of carhaxole homologs are reported uk 1) pica1 examples.
T
HE Craig counterc.iirrc~tit-tlint~~iI~utictn terhnique ( 3 ) i s
iio\v
recognized as a pnwei.fuI t001 for analysis of mistureb of c.iosely related compounds (6-S). In this report the application vi‘ tliis technique to po1ynucle:ir compounds is described. In a. previous study of ttie separation of polynuclear tiydroc:irbons by countercurrent distributioii (d), a solid phase (activated :duniina) was used as one of the immiscible phases becauRe it \viis Thought that the spread aniotig 8-values (ratio of partition coefficients) of polynuclear hydrociirbons in systems composed of t w o liquid phases woultl h~too small to niake clean-cut separaeniploying a solid plixse suc.~~es+ tions. ,ilthough the proc~i:du~~e i’ulI>. wsoived a mirtuic. ( 1 1 :~iithr:tc,c-ne2nd chrysene. i t d i t 1 not
lend itself to e x a c t nutheiii:itic:d in~orptet:ition in icrnis of birequisite for iinalysis and hoinonomial expansion ( 9 )(a iiec~=ssui~y geneity determinations) becxuse of the tendency of partition coefficients to change undull, during the developinrnt of the fract ion:ition procedurv, !Tit ti ttic :idvent o f improved distribution irrstrumcnts c:tpat)le of distinguishing hetween pairs of compounds \vith 8-valucs as Ion :is 1.1 ( 1 , a), it .ippcitred tvorth while to examine possibilities for sep:mtion :rnd estimation of polynuclear cwmpounds by countercurwrit distribution betlveen immiscible liquid pair&. The p:irtition cocfficients of a number of common polycyclic aromatic. conipountls in the system, (~ :mtl c-orrcl:itc~tlw i t h strurturc!. cttij.1 :tIcohol, i v ~ r ni(~:isurcd
