BY 1. R. BEATTIE A N D 11.WVEBSTEK Depai tnient of Chemtslr?J,Kino's College, Strund, London,
1v.c.2
Received Auoust 4 t 1861
The intoraction of 2,2'-hipyridyl and I, 10-phcnanthroline with hydrogen chloride in the prescnco and in thc absence of w:itcr has been examined. The "dihydrocllloridc" of l,l0-phcnanthrolinc is estremcly hygroscopic and in moist air rracts to form thc monohydrate nionohydrochloridc. It appears that 2,2'-rrionohydrochloride is tzsozd cvcn when anhyciroup. 1,I0-I'hci~arlthroline monohydrate in solution in bcnzenc is in cquilibriu~nwith water and the anhydrous base.
The behavior of 2,2'-bipyridyl arid 1,lO-phcn- irito an ethereal solution of 1,1O-phcnanthroliiie :uithroline RS monoprotic bases in aqucous solution monohydratc yields u compouiid with SL chloridc d o w to p H values of thc order of unity is well content corresponding to more than 2 moles of IICl estab1ished.l Thus, the ratio of K , to Ka for the per mole of monohydrate. Howcver, this comcon,jugate acids of 2,2'-bipyridyl is about lo5, arid pound readily loses hydrogcn chloride on warming to it has 'tmn suggrsted that such behavior is due to 4zo, to giye the monohydratc monohydrochloride. hydrogen bonding,2inductive c f f c c t ~and , ~ contribu- Passage of hydrogrn chloridc into asolutiori of I ,IOpheiisnthrolinc in cther under rigidly anhydrous tions from structures such as (I)4 conditions yields tl precipitate which, wheu warmed to 45' in air, analyses for the monohydrate monohydrochloride. However, outgassing in vacuo for 30 '€1 min. gives a compound analyzing as 1,lO-phenan1 thr0line.2.7~HCI. These results can be rationalized These views have been discussed by Wt.stheimci in terms of a very hygroscopic dihydrochloridc and and Bcnfey.6 In the case of I ,lo-phciianthrolinc variable amounts of IIC12- ion, depending on the thc picture is simplificd by the fixed alignnicnt of time for which the hydrogcn chloride was passed. the riiigs. Thc results rcportcd hcrc merc obtained It is clear that the addition of one molecule of during a. study of the products of hydrolysis of the water to the anhydrous hydrochloride involvcs thc additioii compounds formed by these bases with cffective deprotonation of one nitrogen. aiitimony and phosphorus pentahalides. In ordcr that the hydrogen bonding in 1,lO1,lO-I'henanthroline crystallizcs from water as phenanthroline monohydrate could be studied in the monohydrate, with a low vapor pressure.6 It more delail, this compound was examined in soluhas becn suggrstcd that thc water is hydrogcn- tion i n ether aiid benzene. Figure 1 shows the inbonded t,o the nitrogen, although thc frequently frared spectrum of the monohydrate (a) i n cthcr arid quoted cxperirnental evidence for this is light.^ (b) in benzene. The spectrum of water in these sol.lccording to Sakamoto," if gaseous hydrogen chlo- vents a t similar concentrations also is showii. In ride is passed into an ethereal solution of ],IO- the case of the ethcrcal solution the two spectra are phcnnnthrolinc (monohydrate '?) and the product virtually identical (ailhydrous 1,lo-phenanthrodricd ovcr phosphoric oxide for five days, the line has no peak in this region). ITowcvcr, in monohydrate monohydrochloride is obtained. Thcsr bcrrzcne the frcc ~ a t e peaks r in the solution of the results suggest that hydrogen bonding may be of monohydratc arc considerably smaller than thosc importance in determining the base strcngth of the to bc cxpectcd from completc dissociation. Furmonohydrochloride in aqueous solution. Thus, ther, there is a broad peak centered at about 3110 although Saliamoto has pointed out that thc N.. . chm.-' analogous to that found in the monohydrate H distance in 11 is long for adequate hydrogen in the solid state. These rcsults shorn that in the bondiiig, this argument does not apply to 111. strongly hydrogen bonding solvcnt ether the mono/===\ hydrate dissociates completely, or nearly completely, while in the casc of benzene only partial dissociation occurs. Both 1,lO-phenanthroline monohydrate and the corresponding monohydrochloride shoivcd nrgligible weight loss in vacuo. * .(). ' The behavior of 2,2'-bipyridyl contrasts sharply 1 with that of 1,lO-phenanthrolinc. Thus, 2,2'-bi11 H 111 \l:c h i d t tint prolonged passage of hydrogen chloridc pyridyl (which is known to be trans in the solidSand thought to be transoid in solutiong) may be recrys( 1 ) S r c for cxainplc 1'. K n i n i h o l ~ ,J . Am. C h e m . So(:., 73, 3487 tallized anhydrous from water. Corrcsporidingly (111.51); J . Z'hys. Chem., 60, 87 (1056). we find that the dihydrochloride (which is thought (2) 11. 1;. Knott and .1. ( 2 . 13rcckrriridge, Can. J. Chem., 32, 512 (1054). to deviate largely from planarity) crystallizes an(3) Sei! f o r ~ x n n i p l oP. U. Mimn arid J. Watson, .1. Ora. Chcrn., 13, hydrous from conrentrated hydrochloric acid. B O 2 (1948). IIowever, 2,2'-bipyridyl monohydrochloride (which (-1) IC. Nakanioto, .I. Phys. Cham., 64, 1420 (1060). generdly is assumed to be n'soid in aqucous solu( 5 ) I?. 11. JVcutlicinicr and 0. T. Benfry, J . B m . Chern. S o c . , 78, 5309 ( I 95G). tion) crystallizes from water as thr dihydrate. (0) .I. S. Fritz, 1%'. LV. C',igle a n d G . 1,'. Smith, iliid., 71, 2480 (10.t9). 2,2'-13ipyridyl monohydrochloride dihydrate readily
(7) C,. 1,'. Sinitli a n d 13'. .'1 Richter, "Phennntlirolinc r ~ n , l Siills t i t u t d I'licnbritliroliiii: Iridir::stors," C . F. Ginitti Clieniieal ( ' ~ i t ~ i p n Colunihus, Oliiu, 10.41.
~ ,
(9) I . I . 3 I r t i i t t nnrl I : I ) Scliroedcr, A d a C r u s t , 9 , 801 (1930). (9) 1' 1'. I'ri Idinr: a i i d It ,I. LV. Le Yv\ rr, J. Chern Sue., 1811 (1951).
I. It. IJISATTIEAND 191. WEBSTER
Vol. 66
A . R . chemical or recrystallized from water; m.p. 94.595.5’ (the m.p. depends on the experimental conditionsrloaed or open tubes, rate of hc~ating,ratio of m a s of 1,10. phenanthroline to internal volume in a closed tube). The spread of literature values1*for the m .p. of l,l0-phenanthroline monohydrate is undoubtedly largely due to 1088 of watcr. Our given m.p. is the sharpest value obtained by us. I t also is the lowest: anhydrous by vacuum sublimation of the hydrate (the anhydrous material is exceedingly hygroscopic): 2,2’-bipyridyl anhydrous by vacuum sublimation of A.R. material. 1,lO-Phenanthroline monohydrate monohydrochloride w a 6 obtained from 1,lO-phenanthroline monohydrate (about 0.45 g.) in sodium-driecl ether (about 100 mi.)by passage of hydrogen chloride for about 1.5 hr. Precipitate weight corresponded to 2.59 moles of HCI per mole of hydrate (Found: C1, ?1:8. Calcd. for C , Z € I ~ N Z . I I ~ O . ~ . CI, ~ ~ I31.7. C I ; The areciaitate readilv lost HC1 on warmine to 45’ and after 2 hr. i o further I& in weight was obgervcd (Found: C1, * a*...- _._._ 14.9. Calcd. for C ~ ~ H B N ~ . H ~ O . ICl, I C I15.1 : %); m.p., I I 1 1 I 1 1 1 I I ( 1 -I 173-176” (sealed tube). 3XHJ :l50 3700 3300 3500 3700 3900 1,lO-Phenanthroline hydrochloride was obtained from Cm.-l. 1,lO-phenmthroline (anhydrous about 0.40 g.) dissolved in Fig. 1.-(a) T h c infriircd spectra. of: m t c r in ether ether (about 100 ml.) by pamtge of hydrogen chloride (from ; (27.2 mmoles L - 1 ) l,lO-~~heiianthroline mono- concd. sulfuric acid on sodium chloride and dried by phoshydrate in ether (19.4 minoles ( b ) l’he infra- phoric oxide) for about 1.75 hr. The solid waa collected as a red spectra of: water i n benzene -- ; (24.4 mmoles ccritrifumte. wushed with ether and the slurrv (a) ulaced in an oven-at 45’ for 40 min.; ( b ) in vacuo for”3i) I&. The 1. - I ) lIIO-phent~nthrolinemonohydrate i n benzene --solid from (a) correspondcd to CI&N2.H20.HCl (Found: (21.1 minoles I.-]). Cl, 15.3. Calcd. for CirlIeNyI1zO.IICl: C1, 15.1): (‘ b ) to C I J I & ; ~ . ~ . ~(Found: ~ ~ H C C1,’35.05):. ~ loses mater in vacuo to yield the anhydrous com- corresponded 2,2’-BipyridylDihydrochloride was obtained from cthereal pouiid. l‘he ea,% with which 1,lO-pheuaiithrolinc. solution by passage of dry hydrogm chloride (Foiind: CI, 2.7,IICl gains water and loses hydrogen chloride to 3 1 i). Cttlcd. for CIoH8N2.2HCl: C1, 31.0; m.p. 205-225” give the monohydrate monohydrochloride, caoupled (sealed tubcs)). C:f. 150-155’ of Nakamnto.‘ Also from hydrochloric acid (Found : C1, 30.7. Calcd. with the st:ibility of this compound and the free cowrntratcd for CI!IHsN~.211C1:C1, 31 .O; m.p. 20(t2:$5’ (sealed tules)). base moiiohydratc in vacuo, suggests that hydrogen 2,2’-Bipyridyl Monohydrochloride Dihydrate was ohbonding may be of importance in determining the hined from aqucous solution by treatment OF 2,Y-bipyridyl basic behavior of 1,lO-phcrianthroline. The prop- with the calculated quantity of stanchrd iipprosimatcly hydrochloric acid. Long neatlle-shapcd crystals from erties of the analogous 2,X’-bipyridyl compounds molar on a steam-bath (I’ountl: C1, 15.4. Calcd. for shorn that hydrogen bonding is likely to be less im- cvnporation Cl&N~.2H,O.€ICl: C1, 1 5 5 ) ; m.p. 44-45’ (open and portant for these compounds and further indicates, sealed tubes). Analyses-For 2,2’-bipyridyl compounds by dcterminaby analogy with monoprotonated 1,lO-phenanthrotion of chloride gravimetrically as silver chloride. For line, that the rings in 2,Y-bipyridyl monohydro- compounds of 1 ,lO-phenanthroline, the interfering base chloride are not coplanar. had to be removed (before precipitation) by use of the cation exchange resin ZcoICarb 225. TABLE 1 Weight loss.-Zn vacuo 1,IO-phenanthroline monohydrate, 1,lO-phenanthroline monohydrate monohydrochloride and T I I E ULTRAVIOI.I~T SPECTR4 OB (:EIZTAIN Co.\IlWUXI)S O F 2,Y-bipyridyl dihydrochloride d l lost < I ma. pcr hr. on a ~,~’-BIPYRII)YL 50-mg. sample. A 60-mg. sample of Z,B’-bipyridyl mono-Max. (in&N r t h o d or hydrochloride dihydrate lost 10 mg. in 30 min. (Found: Cornpoiindo (1) (11) sol\ e n t C1, 17.9. Calcd. for CioH8NyHCl: C1, 18.4). The nhsence 285 238 IiCl Bipy of water also was shown hy an infrared spectrum of this 285 b CtIC13 compound as a mull in Nujol. e Spectra.-Ultraviolet spectra were determined on a 305 KCI Bipy.2IiCl b CIIC13 Unicam S.P. 500, using either I-cm. vitrous silica cells with 302 chloroform dried over and distilled from calcium hydride, KC1 Bipy.2Ii20~1ICI 302 2 10 or ICCI discs. In the case of anhydrous 2,2’-bipyridyl nionob CHC13 300 hydrochloride, where anhydrous conditions were essential, the spectra in solution were determined using a vacuum 301 2-10 KCl Bipy.EtC1 technique with no taps or joints. For thc solid state spectr:t b CI-ICI, 301 8 dry-box was used. Infrared spectra were determined on a I3ip.v. = 2,2’-t)ipyiidyl. b N o t obscrvcd. \'cry wealc l’erkin-Elmer 221. if present.
.
Table I shows the ultraviolet spectra of 2,2‘bipyridyl inorioliydrochloridc under a varict y of conditions (tho free base and dihydrochloridc are included for comparison). The spectra are virtually identical in all cases for the monohydrochloride, and it appears that the compound is cisoid even in the absence of water. Experimental (A11 melting points are uncorrected.) Reagents .-1 ,IO-Phcnanthroline nionohydrato \vas nn
We thank Dr. C. W. Rees for helpful discussion, the Department of Scientific :und Industrial Research for a grant to M.W., arid for the purchase of a Perkin-Elmer 221 infrared spectrometer, a.nd the Iloyal Society for a grant; to purchase a Unicani SI’. 500.
(10) I. Ifeilbron a n d H. Bunbury, “Dictionary of Organic Compounds,” Eyre a n d Spottiswoode. London, 1953; C. Allen, “Tho chemistry of Heterocyclic Compoun~ls. Six-Membered IIeterocyclic Kitrogen Compounds with Three Condensed Rings.” Interwicncr I’ubl.. New York, N. Y..1958; It. Bclcher, XI. Etacey, A. Sykes und J. C . Tatlow, J. Chem. Soc.. 3846 (1954).
