XL1X.-Researches on the Relation between the Molecular Xtructure of Carbon Cornpounds and their Abso ytion-spectra. (Part IX.) O n Isomeric Cresols Dihydroxybenzenes and Hydroxybenzoic Acids. By W. N. HAKTLEY F.R.S. Professor of Chemistry Royal College of Science Dublin. SAMPLES of the ortho- meta- and para-cresols and of hydroquinone (qninol) pyrocatechol and resorcinol were obtained from Mr. Kahlbaum’s agents. Although they were found to be satisfactory after a single purification nevertheless these specimens were redis-tilled and rendered free from any slight colour which they might have acquired by keeping the final distillation being performed just previous to their examination. The distillates from the para- and ortho-cresols appeared quite colourless just at the moment of conden-sation but a t the lower end of the condensing tube they were observed to be pale yellow in colour in other words though colour-less when hot these substances were colonreil when cold.The meta-cresol became slightly coloured after keeping for some time. The three bodies stand in the following order as to colour :-Metacresol colourless. Paracresol yellow. Orthocresol darker yellow. The specimens of salicylic acid metahydroxyhenzoic acid and pnrahydroxybenzoic acid the spect’ra of which were described in the Philosophical Transactions Part I 1879 were also examined by the method which I have more recently described. It was deemed advisable to recrystallise the two latter substances. They were accord-ingly dissolved by boiling in water ; both formed somewhat brown solutions.Crystals from the solutions were carefully selected washed free from mother-liquor and recrystallised a.s often as it appeared that they gave a slight tinge of colour to the liquid i n which they were dissolved. Finally they were obtained quite free from admixture with other crystals or uncrystallisable matter and appeared as nearly as possible of perfect whiteness yielding solutions quite free from any perceptible colour. The strength of the solutions photo-graphed as in cases latterly described were molecular proportions in milligrams dissolved in 20 C.C. of alcohol. The descriptions of spectra and the molecnlar absorption curves are presented with this note. SO far the law of absorption of rays which it was expected would guide us in the orientation of the substituted hydrogens in the benzene nucleus does not appear to be the same for the hydrocarbons as for the cresols and dihydroxybenzenes.VOL. LlTI. 2 64 2 HARTLEY THE MOLECULAR STRUCTURE OF I n the hydroxybenzoic acids the order of maximum absorption is the reverse of what it is in t8he xylenes. Thus the oscillation frequencies of the most extreme rays trans-mitted by a milligram-molecule of the four classes of isomeric sub-stances are the following :-Oscillatiom Frequencies of the most Refrangible Rays transmitted by a Nilbigram-molecule. Dihpdroxy- Hydroxyben -Xylenes. Cresols. benzenes. zoic acids. Ortho 3611 Meta . . 34433 Mete 3466 Para 3359 Meta . . 3580 Ortho 3413 Ortho 3399 Meta 3080 Para ,. 3537 Para .. 3359 Para 3151 Ortho. 2986 I n the case of the hydrocarbons cresols and dihydroxybenzenes, the 1 4 derivatives exercise the greatest absorption Though they differ from the xglenes the cresols and dihydroxybenzenes follow the same order of transparency ; but the hydroxybenzoic acids altogether reverse the order of the xylenes and differ from the cresols and dihydroxybenzenes. We may assume that the absorption of rays manifested by one of any three isomerides is a measure of its rate of vibration and conse-quently of the dissipation of energy resulting in the formation of the molecule. Hence the following classification is deduced :-Dissipation of Euergy during Fornzcition. Least. Greatest . Xylenes . Para meta ortho Dihydroxybenzeiies . . . . . . Para ortho meta .. . . . . . . . . . . . . . . Cresols Para ortho meta Hydroxybenzoic acids Ortho meta para In the J. pr. Chem. 22 1-45 V. Rcchenberg has given an account of the heat of combustion of the three hydroxybenzoic acids. The substance which erolves the largest amount of heat on combustion must be that by which the least amount of energy was dissipated during its formation and it is worthy of remark that according to v. Rechenberg the hydroxybenzoic acids follow the order of classifica-tion given above namely ortho meta para the heat units evolved beingX 759,000 754,000 and 752,000 respectively. For the curves and measurenients of the three xylenes see Trans., 1885 48 702-749. For explanations of the plates see Trans, 1887, 51 201. * These numbers are taken from Pattison-Muir’s Elements of Thevmal Chemistry p.65. Macmillan 1885 OURVES OF MOLECULAR VIBRATIONS. SALIQYLIU AOIO (NATURAL) .-.-.-.-.-METOXYBENZOIC AOlO *-PAROXYBEHZOIC AGIO *** -- _____c_ IL 0 Scale of Oscillation - Ihquencies Harmon & Sons Lith. S Martins > axe.% C OURVES OF MOLECULAR VIBRATIONS. . . -.-.-I --.- 1.4. QU I N 0 L a . . PYROCATECHOL * .-------- 1.2. RESORCINOL * a * .- 1.3. TIM GUWCI of Pytmattclwl and Rcrorcinol run me into the other al tAe point8 marked thur ORTHOCRESOL C6H4(CH3)*OH 1 2. 0.108 gram in 2890 *3 3480 2364 - 2890.3 to 2444 3480 to 4016 - 4253 ~ ~~~ Thickness of layer of liquid 2875 Description of spectrum, ----Continuous spectrum to. Absorption band from Two very feeble lines at., ,) . Feeble spectrum to . Thickness of layer of liquid,. Continiious spectrum to . Absorption band from Feeble spectrum to . Faint spectrum to w 5 mm. Oscillation frequencies. --3413 3413 to 4125 4125 4136 -Wave-lengths. 2930 2930 to 2424.3 2424.3 2418 -2 mm. 3460 3460 to 4093 4232 -4 mm. 3439 3439 to 4125 12906.5 I I 4G5 1 1 mm ~~ ~ ~~~~ Thickness of layer of liquid Continuous spectrum to . Faint spectrum to Weak spectrum to . Absorption band from 5 mm. 3493 3493 to 4016 4253 -Description of spectrum. 3493 3493 to 3890 4253 Oscillation frequencies. 2863 Continuous spectrum to . Absorption band from Wave-lengt,hs. 3525 2836 *5 3525 to 3832 2836'5 to 2609 2863 2863 to 2490 2352 -Thickness of layer of liquid 2 mm.Very feeble spectrum to -Weak spectrum to . 1 4331 - 1 2310 4 mm. 3531 1 (Absorption band but rays are very feebly between lengths 2831 and 3768 4331 1 ORTHOCRESOL-continued. 0.108 gram in 500 ~ontinuoua spectrum to. I 8531 3768 4331 Very feeble spectrum to . I Weak apectrum to 1 i - But feeble t o . . Thickness of layer of liquid 2831 *5 2653 2310 -5 mm. Continuous spectrum to. Spectrum extends to But faint to 4 mm. 4426 9 2259 3768 2653 L I I -I-l- I-~-I Same aa last. I I I Thickness of layer of liquid. . 2 mm. 1 mm. I 4426 * 7 466 METACRESOC C6H4(CH3)*OH 1 3. 0.108 gram in 20 C.C. alcohol. Oscillation frequencies. ~~ Thickness of layer of liquid,.Wave-lengtbs Description of spectrum. ---3433 3433 to 4125 4125 4136 -Continuous spectrum to . Two very feeble lines at . Two weak lines a t . . Absorption band from,. . . 9) . . . . . . . . . . . . . . . . . 1 ) 2912 -5 2912.5 to 2424: 2424 -3 2418 -I Thickness of layer of liquid Thickness of layer of liquid . , Continuous spectrum to,. . Absorption band from Spectrum extends feebly to 5 mm. 5 mm. 2 mm. 3460 I 2890 -3 4190 1 2387 3460 to 4125 2890.3 t,o 2424.: 4 mm. Oscillation frequencies. 3460 3460 to 4125 --4125 4136 Vave- :::::;, -2890.3 1 mm. 4190 METACRESOL-continued. 0.108 gram in 100 4 mm. Continuous spectrum to . 3493 2863 3493 Absorption band from 3493 to 3890 863 to 2568 3493 to 3890 2863 Spectrumextends to I 4190 1 2387 I 4253 ~ Thickness of lager of liquid Continuous spectrum to .. . . . . . . . . . Feeble spectrum t o . . . . . . . . . . . . . . . . . Spectruni extends to 2 mni. 3531 3768 4331 1 mm. Spectrum extends to. Continuous spectrum to. . . . . . . . . . . . . 1 3525 2836 - 5 3531 . - - 3768 Spectrum extends to . . . . . . . . . . . . . . 4253 2352 4331 Feeble spectrum t o . - Absorption band from . . . . . . . . . . . . . . ~ 3525 to 3768 2836 -5 to 2653 I 4426 *7 I 2259 &fETACREsoL-co?ttinzted. 0.108 gram in 500 Thickness of layer of liquid,. . 5 mm. 2836 -5 2653 2310 Thickness of layer of liquid 2 mm. 4 mm. 1 mm. 4660 PARACHES~L C,H,(CH,).OH 1 4.0.108 gram in 5 min. Oscillation frequencies. Wave-lengths* --3359 2976 * 5 4125 2424 '3 4136 2418 - -3359 to 4125 2976'5 to 2424'3 Thickness of layer of liquid . 4 mm. Oscillation frequencies. Wave--Same as last. Description of spectrum. 3392 3392 to 3890 4163 Continuous spectrum to. . Absorption band from . Two very feeble lines at . Spectrum extends to )) 3 9 . 2948 Thickness of layer of liquid Continuous spectrum to. Absorption band from Spectrum extends to Thickness of layer of liquid 5 mm. 4 mm. I 1 mm. I 2 mm. Same as last. Continuous spectrum t o . . . Absorption band from . Q,.-L -- - - L - - d - 4 3392 1 2948 I A 1 QZ Oion 3392 to 3890 2948 to 2658 Same as last. UUGVUI~UILI GAWUUJ L U .. I XLUU I YUilU I I I 2 mm. Thickness of layer of liquid ! Thickness of layer of liquid. 1 mm. 5 mm. Oscillation Description of spectrum. frequencies. Wave-l%ths. Continuous spectrum to . Very feeble spectrum to . Spectrum extends to. Continuous spectrum to. 3392 2948 Absorption band from 3392 to 3832 2948 to 2609 Very feeble spectrum to . - -Spectrum extends to 4232 2364 3426 3768 4253 I Spectrum extends to 3426 -3’768 4253 4331 1 2310 2018 * 5 2653 1 2352 4 mm. Same as last. I Thickness of layer of liquid. 2 mm. 1 mm. 4660 PYROCATECHOL C,Il,(OH) 1 2. 0.110 gram in 20 3460 3460 t o 3890 4253 Thickness of layer of liquid 5 mm. 2890.3 4 mm. Continuous spectrum to . 3460 Absorption band from 3460 to 4016 Weak spectrum to 4136 -~- -Continuous spectrum t 0.. . . . . . . . . . . . I 3399 1 2942 I 3413 2890 '3 2890.3 to 2490. 2418 Thickness of layer of liquid. . Continuous spectrum to. . . . . . . . . . . . . Absorption band from Two weak lines a t . . . Weak spectrum to . . . . . . . . . . . . . . . . . 9 ) )) 2 mm. 1 mm. 3439 2906 -5 4125 2424.3 4136 2418 3439 to 4125 2906'5 to 2424, 3460 3460 to 4016 2890.3 - -4136 P Y R o c A T E c H o L - c o ~ t i e ~ . 0.110 gram in 100 4 mm Thickness of layer of liquid Thickness of layer of liquid 2 mm. 4 mm. 5 mm. 1 mm. Continuous spectrum to. ~ 3531 2831 *5 Absorption band from ~ 3531 to 3768 2831.5 to 2653 Weak spectrum to 1 4331 2310 . Paint spectrum to,. - - Description of spectrum.3’768 3531 -4374$ -4 I Oscillation 1 Wave- frequencies, . Thickness of layer of liquid Continuous spectrum to Very faint to Continuous spectrum to. ~ 350’7 2852 *3 Absorption band from 3507 to 3832 2852 3 to 2609 Weak spectrum to 1 4331 1 2310 4426 #? Same as last but stronger. I 4660 I 1 mm. I 2 mm. -I- I 3531 3531 to 3’768 2831.5 I 4331 I I 1 RESORCINOL C,H,(OH) 1 3. 0.110 gram in 20 3507 3507 to 4125 4125 4136 -Thickness of layer of liquid 2852 -3 2852'3 to 2424.: 2424 -3 2418 -Description of spectrum. ' Continuous spectrum to. Two faint lines at . Absorption band from ¶ > ,) Thickness of layer of liquid Continuous spectrum to. Two weak lines at Absorption band from .Weak spectrum to )> )) . ~ 5 mm. I 2 mm. 4 mm. 1 mm. 350'7 to 4016 2852.3 - 3507 1 -4163 RESORCINoL-con~~nz~ed. 0.110 gram in 100 I 1 4 mm. I Thickness of layer of liquid 5 mm. I I I I I I Continuous spectrum to. 350'7 2852 -3 3531 Absorption band from. 3507 to 4016 2852'3 to 2490.5 3531 to 3890 2831.5 Weak spectrum to,. 1 4163 1 2402 I 4253 1 I Thickness of layer of liquid,. . Continuous spectrum to. Absorption band from . Very faint to Weak spectrum to,. 2 mm. 3537 1 2826.5 - I 3537 to 3832 2826’5 to 2609 4253 1 2352 1 mm. 3580 3768 --4374 -4 Description of spectrum. , Oscillation Continuous spectrum to . 3537 3647 Faint spectrum t o . . I Absorption band from I 364’7 to 3’768 Weak spectrum to .. . . . . . . . . . . . . . . 4331 Very faint to . 1 -I I- -___-2826 5 274Q -2’740 to 2653 2310 Thickness of layer of liquid Oscillation frequencies. 2 mm. 3537 3647 364’7 to 3’768 4331 Continuous spect,rum to . Faint spectrum to 3’768 3 580 Weak spectrum to . . . . . . . . . . . . . . . . . . 4374.4 Wave-2’793 2653 2286 2740 REsoRcINoL-contilzzced. 0.110 gram in 500 Thickness of layer of liquid . 5 mm. 4426.7 4660 QUINOL C6H4(OH) 1 4. 0.110 gram in 20 C.C. Alcohol. Continuous spectrum to . Very feeble discontinuous to Absorption band fi-om Faint discontinuous to Thickness of layer of liquid ~ - ~~ . I 5mm* I Thickness of layer of liquid. 3151 1 3171 - -I - I - -I 2 mm. Description of spectrum.Cont,inuous spectrum to. 3151 3171 Absorption band from 3151 to 3890 Weak discontinuous to. . 4050 Continuous spectrum to . ~~~~ 4 mm. I 3171 to 3568 2469 ‘5 -1 mm. 318’7 3187 to 3832 4125 -QUINOL. 0.110 gram in 100 C.C. Thickness of layer of liquid 5 mm. Continuoils spectrum to 318’7 3 140 Absorphon band from 3187 to 3832 3140 to 2690 Continuous spect,runi t o . 1 4125 I 2424’3 318’7 3187 to 3832 4136 314 Thickness of layer of liquid, . . 2 mm. Thickness of layer of liquid, . 1 mm. 5 mm. Description of spectrum. 3320 3320 to 3500 4190 Continuous spectrum to 3194 3130 Absorption band from 3194 to 3701 3130 to 2701 Continuous spectrum to I 4136 1 2418 3014 3221 to 3647 3104 41 36 3221 I Thickness of layer of liquid QUINOL.0.110 gram in 500 C.C. 2 mm. --4660 I I Cont,inuous spectrum to 3297 3033. Absorption band from 3297 to 3531 3033 to 2831 -5 Continuous spectrum to I 4190 1 2387 Continuous spectrum to 3359 2976.5 Absorption band . 3359 to 3493 2976.5 to 2863 Spectrum extends to . . . . . . . . . . . . . . I 4331 1 2310 4 mm m W cn Q) 03 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E : ,o .o,o In P Thickness of layer of liquid 2 n -I I 2 mm. I Description of spectrum. Thickness of IaFer of liquid Spectrum ext,ends to 3066 3261 Absorption band from 3066 to 3641 3261 to 2’744 -5 Rays transmitted t o . . 1 3970 I 2518 4 mm. I 5 mm. 1 mm. Spectrum extends to .Absorption band from Rays transmitted to . 3080 3245 -5 4028 2482.5 3080 to 3525 3245.5 to 2836 3151 3151 to 3494 31’ 4033 I Oscillation frequencies. I- -4130 4415 4130 to 4326 2421 3080 3080 to 3525 3245.5 4028 I I tQ 4 Spectrum extefids to Absorption band from Rays transmitted to SALICYLIC AcID-continued. 0.138 gram i n 500 4033 24’79 * 5 - -- -Thickness of layer of liquid 2 mm. I 1 mm. SAIJCPLIC Acm-continued. 0.138 gram in 2500 C. Oscillation frequencies. Thickness of layer of liquid. . . . . Ware-5 mm. Thickness of layer of liquid . . . . Oscillation frequencies* Wave-lengths. I i Description of spectrum. 2 mm. Spectrum extends to . . . . . . . . . 242 1 Absorption band from . .. . ,. . . . . . . 2421 to 2313 Rays transmitted to ,. . . 1 4415 I 2265 4130 4130 to 4326 Thickness of layer of liquid . . . . 5 mm. 4 mm. Spectrum extends to. . . . . . . . I. . . . 3080 I 3245 *5 3080 I ~~~~~ ~ ~~ Spectrum extends to. . . . . . . . . . . .I 4658 1 2148 -5 41 mm. I- --4i30 4550 1 4130 to 4243 2421 I 1 mm. 4658 1 The solution 0.138 gram in 20 C.C. gave a brilliant blue fluorescence decreasing diluted Thickness of layer of liquid 3115 3115 to 3641 3885 2 mm. 3208 1 mm. oscilla'tion Wave-lengths. frequencies. 1 i Description of spectrum. Spectrum extends to 3245 *5 Rays transmitted to Absorption band from Thickness of layer of liquid fi Spectrum extends to Absorpt,ion band from w + Rays transmitted to .I I 2 mm. Same as 3 mm. METAHYDROXYBENZOIC ACID-continued. Thickness of layer of liquid. . . I 5 mm. Spectrum extends to 3080 3245 *5 Absorption band from Rays transmitted to I 3885 1 2572 3080 to 3826 3245 . 5 to 2613 I I i Oscillation frequencies. wave-3080 to 3826 3245 1 3885 3885 0.138 gram in 100 318'1 1 3187 to 3568 3914 3140 &IETAHYDROXPBENZOIC ACID-continued. Thickness of layer of liquid. 0.138 gram in 500 5 mm. -Spectrum extends to Rays transiuitted to Absorption band from I I - I ---318’7 3140 3914 2553 318’7 to 3568 3140 to 2802 *5 Description of spectrum. 3221 3221 to 3494 39’70 3104.5 I I I -4055 4055 to 4311 4420 Thickness of layer of liquid 2 mm. 2466 1 I I Thickness of layer of liquid Spectrum extends to 4028 2488 -5 Absorption band from I Rays transmitted to 5 mm.Spectrum extends to 1 4055 4055 to 4311 Rays transmitted to 4420 Absorption band from 2466 2466 to 2321 2263 4 mm. 4055 4055 to 4311 4420 2466 4 mm. 0.138 gram in 250 Thickness of layer of liquid . . , , Description of spectrum. Thickness of layer of liquid . . -Spect.rum extends t o . . . . . . . . . . . . . Absorption band from . . . . . . . . . . . . . . Rays transmitted to . . ,. . . . . . , 1 mm. 2 mm. 2 mm. I 1 mm. 2450 4658 -4555 2195 -Slight blue fluorescence. PARAHYDROXYRENZOIC ACID C,H,(OH).COOH 1 4. 0.138 gram Thickness of layer of liquid. . . PARAHYDROXYBENZOIC Acm-contiiizced.Thickness of layer of liquid Thickness of layer of liquid. 2 mm. 5 mm. Thickness of layer of liquid J -I I 5 mm. 4 mm. Description of spectrum. Spectrum extends to . 3525 Absorption band from 3525 to 4415 Rays transmitted to - 2836 *5 2836.5 to 2265 -Spectrum extends to 3500 2857 -5 - Absorption band from 0.138 gram in 100 4 mm. I ---3500 I 1 mm. 3525 4415 1 3525 to 4326 2836. 1 I Description of spectrum. Thickness of layer of liquid. Spectrum extends to Absorption band from Rays transmitted to 2 mm. 2744 -5 3641 to 4306 2744.5 to 2323.; 4415 3fi41 1 2265 --1 mm. l-l--3641 to 4297 2744.6 45 3641 50 1 3641 3641 to 4291 4550 2744 * 5 2744 -5 to 2329 2197 3885 3885 1 o 4179 4658 ~ 2572 2572 to 2393 2148 *5 Thickness of layer of liquid.. Spectrum extends to Absorption band from Rays transmitted to Thickness of layer of liquid Spectrum extends to. Absorption band from Rays transmitted to 5 mm. 4 mm. Same as 5 1 mm