1084
1-01. 64
SOTES
ity coefFicieiit factor essential to correcting the latter can he included in the constant term in eq. 1 and is probably not highly significant since the solutions used were dilute, the ionic strength was kept constant, and the activity coefficients have only a small temperature dependence. The msential constancy among these AH va1ue.i indicatthq chemical similarity among the three primary amine nitrogen atoms. The AH values for the three dissociation steps of the trihydrochloride of diethylenetriamine are, respectively, 11.1, 12.25 and 7.6 kcal./mole.6 If the first, two are assigned t o the -SH,+ groups a t the end of the chain, agreement with values for the structurally analogous groups in the hydrochloride of p,p',P''t naminotriethylamine is quite satisfactory. (0) 0. I[. JIcIntyre, ,Jr., B. P. Blork and W. C. rernelius, C h e m SOC81, 5 3 (1959).
.I A m
THE EFFECTS OF T E M P E R h T U R E OK T H E DISSOCIhTIO?; COSSTAXTS OF SOME COUI'LEXES OF T H E T Y P E R2Se.121 B Y J. 1). ~ I C ~ C L L O AND UGM IRMELA c. ZIMMERMASY D e p a i t m e n f n/ Chemzstiu of the Cnzuersitu of Calzfornza at Lo8 A n g e l r s , L o s Angeles. Cal.
In the first cycle, the ahsorbance corrections arc made on the assumption that a11 of the selenide slid iodine are 1111combined, ix.,K, = m . This leads to tentative values far and K,. I n subsequent cycles the conccntrations of uncombined selenide and iodine are computed on the basis of the K, from the previous cycle. The computing routine continues these least-squares cycles until the change in K , is inappreciable. All significant quantities from each cycle are printed out so that the progress of the calciilatioii can be followed. Three or four rrrlrs are normallv sufficient. The equilibrium constants ohtainrd in this W L ~are given in Table I.
VALVESOF IC, X(nic)
TABLE I R2Pe.12AT VARIOUSTEXPER~TCRES ASD WAVELENGTHS
(a)
R
2,500 2, i n 0 2,850 2 , 860 Av. (11)
Experimental The preparation and piirifiration of materials and the experimental procedures have been described in the earlier communications For each complex some eight to trn solutions were prepared covering a wide range of ratios of selenide t 3 iodine. Several spectrophotometric recordings were made of each sample a t each temperature. The data for each complex at each temperature and a t each of several wave lengths were fit to the eqiiation SHIIA1, = (S H - C)/e Kc/c (1) This equation is a modification of that suggested by Scott . 3 In Equation 1 the svmbols have the meanings noted: S and H are the formal or total Concentrations (in moles per liter) of the selenide and iodine, respectively, C is the molar concentration of the romples at equilibrium, A , is the absorbance of the soliition, corrected for absorbance due to tincornbind iodine and iincombined selenide, 1 is the optical path length in cm., e is the molar absorptivitv (extinction coefficient I of thcA complex and K, is the dissociation ronstant in moles per liter. In the above form, the equation is not restricted to the condition S>>H as it is in the form given by Srott . Equation 1 represents a straight line if SHl/A, is plotted against (S H - C). The slope of this line is 1 / e and the intercept i. K e / e The experimental data for each complex at a given remprratiire and wave length are fit to the straight line represented hy equation 1 bj- a cyclic least-squares routine on the TALI 709. In each cycle the observed ahsorbance is corrected for the ahsorbance due to uncombined selenide and iodine and the least-squares line is obtained.
+
+
(1) This research was sponsored by the National Science Foundation under Research Grant NSF-G5922. (2) J. D. \IcCullough and Denise Mulvey. THISJOURNAL, 64, 264 (1960). Reierences t o earlier work are given in this paper. (3) R. L. 3cott, Rec. trav. chtm., 7 6 , 787 (1956).
( K c X IO3),
15.30
.35.80
~18.4'
1.1 1.1 1.1 1.2 1.12
3. I 3 ,2 3.2 3 ,0 3.17
5.6 5.8 5.3 5,2 5.43
R = p-nicthoyyghenyl ( K r X 10')
X(mc)
c
15.80
370 380 390
16,500 16,700 14,900
0.93 0.95 0.96 0.947
Av.
R = p-toiyi
(c)
Dissoc4ation cwnstants in carbon tetrachloride Folutioii at 25" for eleven complexes of the type R2Se.1 2 have been reported in previous communications from these laboratories.? The present communication reports a study of the dissociation constants of four representative complexes from this group over a range of temperatures in order t o permit calculation of values for AHc0 and L\S," for the disqociiitions.
= methyl
e
420 430 410 450
Rerezied .l/mich 8, 1960
+
FOR
wc x
X(mc)
6
lfi.Oo
350 360 3 70 380
18,100 20,100 19,400 16,900
1.5 1.0 1.7 1.7 1.63
Av. X(mr)
350 360 370
R
(rl)
= p-chlorophengl
15.70
6
16,200 13,100 10,400
1.OO 0.86 0.81 Av. 0.89
:lii.RO
4-1 . -.IO
2 , :+ 2 .0 2 .3 2.20
3.6 3.6 3.6 3.60
102) 30. I O
45.00
5.0 5 .1 5.2 :3 . 4'-Dirreth!.ldiphenylseleiiiiim In 2 . 1 9 6 . 9 16.4 Diphen\~lst~I(~iiiiiiii In 1.Yi .. .. 4,4'-Diclilorodi!,ht.nJ.lselenium 1, 1 . 2 6 4 . 2 10.0 Prcsent stiitlJ-.
rrystctllinc~soiids \vliilth thv quilil)ri:t \vrrc stiltlied in diliitc, solution. Ti,(. striwturw of the complexes in solution arc accordingly :uhjcrt to some uncertainty. The reported values of AH;' and AS;] for 4-chlorodipheriylselenii1m ditlromide suggwt that thme are too high and that they should be redetermined.
1085
drawing groups decrease and electron supplying groups increase the reactivit'y of the a-hydrogen at'oms of cumene or t,oluenetoward a peroxy radical. It has also been s h o ~ that' n ~ electron-withdrawing groups decrease the rate of reaction of benzaldehyde with peroxy radicals. The above work would seem to confirm the work of Rigg and Gisser' wherein they stat'e that, the rate of oxidat.ion is due to t.he proximity of t'he oxidatmionsite tlo areas of high or low elect'ron density. If t'he osidat'ion rate is dependent on t'he proximity of tertiary carboiis to centers of elect,roii uggested by Rigg and Gisser,' the effect. observed by them n-it,h esters should be reversed in the oxidation of compounds having a n electron releasing group instead of the ester group. To accomplish this, several methyl-l-pniet'hoxyphenylalkanes (which hare a high electron densitmyat, t8he carbon atom a,d,jacent,to the hellzene ring) were prepared in which the di&iire of the tertiary carhon atom froiri t'he ring iixs i.xrittl, and t'heir autoxidation rates studied. Experimental 1-Methyl-1-p-methoxyphenylbutane\vas prcqxtred l)y tht: method or Tsiikervanik and Saz:trova' from :misole and
pentanol-2 with anhydrous aluminum csliloride. The distilled material xas collected a t 81-82' :it 3.5 mm. The yield was 120 g. (25%), n,% observed 1.49865, reported 1.499. Anal. Calcd. for C12H180:C, 80.85; H, 10.18. Found: C , 80.35; H, 10 16. 2-Methyl-1-p-methoxyphenylbutane WBS prepared from p-methosybenzyl bromide and sec-but;\Imagiic,siiiin bromide. The distilled material was collected a t 82-84" s t 2 mm. The yield was 84 g . (25%), n% observed 1.49982. A n a l . I I I I O I I ~ I aI n d 31. K. R a w h , ihid., 71, 8029 (lU4U). Palcti. for ('IPHIXO:C, 80.85; 1-1, 10.18. Found: C, iilluiigli, h i d . , 64, 2G72 (1912). 81.43; II,R.i4. 3-Methyl-1-p-methoxyphenylbutanewas prc~parcd in :L nianner siinilitr to l - m e t h ~ l - l - p - n i e t h o s g p h e ~ i ~ l ~ ~ i t a ~ ~ e ~ from anisole arid isoamyl c-hloridr. Thci distilled material THE .ICTOSIDL~TIOKOF was rollected a t 78-79' at 1.25 mm. The yield \vas 70 g . 34E:T H OSYPHESYLA 1,k'ASE S (IO%), n 2 0 i ) observed 1.50752, rrported 1.51 12. rlnal. C'nlrd. for C12H,0: C, 80.85; H, 10.18. Foiind: C , 81.28; BY A. ~ \ : E R T W O Y ,11. TRACHTJIAK ASD H. GISSER 13, 9.95. 4-Methyl-1-p-methoxyphenylpentane was prepared in :t P i t m a n - D u n n Laboratories. F r a n k f o r d Arsenal. L'. S. A r m y Ordnance maimer similar to 2-methyl-1-p-methosyphenylbiitanefroni Corps, Philadelphia 57, P a . isoamylmagnesium bromide and p-methoxybrnzyl bromide. Reeeii.ed March 16, 1960 Thtl distilled material was collected at 125-127' at 9.0 mm. In the autosidation of branched chain amyl adi- The yield was 91 g. (500;), n% observed 1.4:-524. .4n,ul. C a l d . for C!lnH210:C, 81.25; €1, 10.42. Found: C, 81.28; pates1 it, was observed t,hnt t'he dist'ance of the ter- 11, 10.30. tiary carbon atoni from 1,he ester group exerts a Bis-( 1,3-dirnethylbutyl)adipate W:M prcpirrxcl 13). mtwicwisiderabli~effect, o n tlie oxidatioii r a k , the rate fir:+tion of I ,:i-dimothylhut~.li~l~wliol:tiid :trlipic, iicitl with decreasing as the cli.~t:tiiccis decreased. The dif- a ratxlytic- qu:iiitity of p-toliiriit,srilfoiii(~:wit1 inonohydratr'. m t w u.erc2 clrterniined h,v nic'xsiirference in the oxidatioii rate \\-as attribut'ed to resoc*onsiimptiori iieing thtl :tpparrttiis nance at, t,lie ester groiip which m d e electrons less d(wriht:d. Thcj r a t w of oxidation stvailahle t.c-3 t'he tertiary cxrbon atom :is it moves of t hc mrt h ~ l - p - i i i e t h o x ? p l i ~ ~ ~ ~ y\vvrv l ~ l l ~ti(~terniinrd ~ i ~ i ~ ~ s :it .If ('Oppc'r 2-('thy1 ll('S(J:tt progressively rlowr to the est,er group. 111 t
