March, 1946
COMMUNICATIONS TO THE EDITOR
535
Since our method of cleaving the dimethyl When n is finite, the BET theory does not preether gives comparable, if not better, yields of dict complete filling of capillaries at saturation pure 3-n-pentadecylcatechol, and takes less time pressure. This is generally considered to be an and effort than the procedure described by Mason, unsatisfactory feature of the theory. Pickett’s i t seems worth while to outline it here in some modification eliminates this feature and seems to improve the range of agreement with experimental detail. The cleavage of the 3-n-pentadecylveratrole to data in a number of cases. yield pure 3-n-pentadecylcatechol was best acThe equations obtained by Pickett follow from complished in the following way. Three grams of his assumption that there is a “decrease in probthe veratrole compound, 3 g. of anhydrous alumi- ability of escape from an elemental area covered num chloride and 30 cc. of dry chlorobenzene were with n layers (the maximum number possible in refluxed for three hours, cooled, poured on ice, the limited space) as adjacent elemental areas washed with SO(;& iiiethanol solution, and the also become covered with n layers.” Specifically, chlorobenzene layer evaporated under vacuum. he assumes that the probability of escape from The residue on molecular distillation yielded 2.5 the n-th layer is reduced by a factor of 1 - x . I t g. (91yc)of crude catechol compound melting a t is pointed out that there is an alternative but 52%59’. Xfter three recrystallizations from pe- logically equivalent way of expressing this assumptroleum ether, 2.1 g. (76%) of pure 3-n-penta- tion. Since the two alternatives are equivalent decylcatechol melting a t 59-60’ was obtained in we shall confine our attention to the first statethe form of short white needles. ment, given above, as i t is more amenable to Anal. Calcd. for C21H3602: C, 78.69; H, analysis (the second statement has a certain intuitive appeal but is more difficult to interpret). 11.32. Found: C, 78.97; H, 11.30. It appears to the present writer that Pickett’s In the conversion of o-veratraldehyde to pure assumption can be criticized on the following 3-n-pentadecylcatechol, an over-all yield of 57% grounds : was obtained. (1) If there is a decrease in probability of escape During the past two years we have been using 3-n-pentadecylcatechol as a standard agent for the from an elemental area covered with n layers as diagnosis of poison ivy hypersensitiveness and for adjacent elemental areas become covered with n demonstrating cross reactivity between poison layers, there is also a decrease in probability of from ivy and other members of the a n a c a r d i a ~ e a e . ~escape ~~~~ ~ ~ elemental areas covered with 1, 2, 3 The optimal concentrations for these tests were . . ., layers as adjacent elemental areas become found to lie between 0.1 and 1.0% in a suitable covered with n layers. ( 2 ) If there is a decrease in probability of escape non-irritating carrier such as acetone or isoamyl (rate of evaporation) as adjacent elemental areas acetate. become covered with n layers, there is also an (5) Keil, Wasserman and Dawson, Science, 102, 279 (1945). identical decrease in the rate of condensation, (6) Keil, Wasserman and Dawson, Indust. M e d . , 14, 285 (1945). according to the principle of microscopic reversi(7) Keil, Wasserman and Dawson, J. Allergy, 16, 275 (1945). DEPARTMENT OF CHEMISTRY CHARLES R. DAWSON bility. Hence, multiplying only the right-hand COLUMBIA UYIVERSITY DAVIDWASSERMAN member of the equation UNIT HARRYKEIL SKINASD CANCER XEWYORKPOST-GRADUATE MEDICAL SCHOOL AND HOSPITAL XEWYORK,N. Y. RECEIVED SEPTEMBER 24, 1945 CONCERNING A PROPOSED MODIFICATION OF THE BRUNAUER-EMMETT-TELLER THEORY OF MULTIMOLECULAR ADSORPTION
Sir: In a recent paper, Pickett’ proposed a modification of the BET2 theory of multimolecular adsorption. This modification does not affect the familiar equation 21
- =
z’m
CX
(1 - x ) ( l - x
+ cx)
(1)
which holds for adsorption on a free surface. It applies, rather, to adsorption in those cases where the maximum number of adsorbed layers ( n )is restricted. (1) Gerald Pickett, THISJ O U R N A L , 67, 1958 (1045). (2) S. Brunauer, P. H. Emmett and E. Teller, ;bid., 60, 300 (1938).
as,-$
= bs,e-EL/RT
(2)
by the factor 1 - x is not justified. The same is true if, in Equation ( 2 ) , n is replaced by 1, 2, 3, . . . (when n is replaced by 1, EI, is replaced by El). ( 3 ) Even if the multiplication of the right-hand niember of Equation ( 2 ) by a factor were justified, the function 1 - x seems to be advantageous only because i t has (a) simplicity, (b) “correct” boundary values, and (c) i t allows the fundamental assumption to be restated in the alternative form mentioned above. (4) A treatment of the problem, using statistical mechanic^,^ leads to the BET result rather than to the result obtained by Pickett. In the statistical treatment, no assumptions regarding mechanism need be made. I t suffices to consider only possible states of the system. The conclusion of the present writer is that, although Pickett’s equations may improve the agreement with experimental data in some cases, (3) T. L. Hill, J . Chem. Phys., in press.
536
COMMUNICATIONS TO THE EDITOR
Vol. 68
his modification should not be considered a really fundamental improvement over the BET theory.
acetylation, yielded pentaacetyl-N-methyl-d-glucosamine; m. p. 160.5-161.5° (micro-block), [CX]"D + l o l o . The properties of this compound DEPARTMENT OF CHEMISTRY UNIVERSITY OF ROCHESTER TERRELL. L. HILL are identical with those of the pentaacetyl derivaN. Y. ROCHESTER, tive described above except for the sign of rotaRECEIVED DECEMBER 10, 1945 tion. With these data and the reported configuration it is concluded of carbon atom 2 of d-gl~cosamine,~ STREPTOMYCES ANTIBIOTICS. V. N-METHYLthat the configuration a t carbon atom 2 of the I-GLUCOSAMINE FROM STREPTOMYCIN hexosamine is also that of 1-glucose and the degraSir: dation product is N-methyl-Z-glucosamine. Streptomycin has been degraded to a new ( 5 ) Haworth, Lake and Peat, J . Chem. SOC.,271 (1939). product which has been established as N-methyl-lFREDERICK A . KUEHL,J R glucosamine. EDWXH. FLYNN Acid hydrolysis of methyl streptobiosaminide MERCKRESEARCH LABORATORIES FREDERICK W. HOLLY RALPH hfOZIh-GO dimethyl acetall followed by acetylation yielded a MERCK& Co , I s c . SEW JERSEY ?&4RL FOLKERS pentaacetyl derivative of a hexosamine; m. p. RAHTVAY, RECEIVED FEBRUARY 26, 1946 160.5-161.3' (micro-block), [ c u ] ~ ~ D- 100' (c, 0.7 in chloroform). Anal. Calcd. for C17H25Nolo: C, 50.62; H, 6.25; N, 3.47; CH,CO, 53.3; NEIGHBORING GROUPS AND REACTIVITY mol. wt., 403. Found: C, 50.51; H, 6.24; IT, .3.76; CI&CO, 49.2; mol. wt., 414 (cryoscopic in Sir: benzene). The hydrochloride of the hexosamine Heretofore, we have stressed the stereochemical was obtained from the pentaacetyl derivative by consequences of participation by neighboring hydrolysis with hydrochloric acid; in. p. 160-163' groups' such as OAc, Br, OCH3, etc., in replace(micro-block), [ a I z 5 D - 103' (initial), -88' (final) ment reactions. We have recently completed rate ic, 0.6 In water). Anal. Calcd. for C71-I15iY05~ measurements which bring out the striking connecHCI: C, .3G,GO; H, '7.02; CHON,6.5. Found: tion between reactivity and this participation. C, 36.65; H, 6.&6; CH3N, G.S. Treatment of the First order rate-constants of solvolysis a t '73' hydrochloride with silver oxide gave the free base in glacial acetic acid of a series of 2-substituted as a colorless gum; [ c ~ ] ~-65' ~ D (c, 1.O in methacyclohexyl p-brgmobenzenesulfor7ates give the nol). Acetylation of the free base in the pres- following relative reactivities : unsubstituted, ence of methanol gave the N-acetyl derivative ; 1.00; trans-2-OXc, 0.240; tram-2-Br, 0.101; m. p. 1153-166' (micro-block), [ a I z 5 -51' ~ (c, trans-2-OCH3, 0.057; trans-2-C1, 4.9 X 0.4 in water). cis-2-OL%c, 3.8 X cis-2-OS02C6H4Br,7.7 X The phenylosdzone prepared from the hexostrans-2-OS02CsH4Br,6.9 X Similarly, amine melted a t 205' ( ~ a p i l l . ) . ~4 phenylosotri- acetolysis rates a t 23.6' of cyclohexyl p-tolueneazole, prepared3 from this osazone, melted a t the sulfonates give the relative reactivities : transsame ternperature (196-197') as the correspond- 2-1, 1800; unsubstituted 1.00. ing derival ive of d-glucose, and the speciiic rotaThe effects of a halogen substituent similar tion was of equal magnitude but opposite in sign. to those above are seen also in the rough values Oxidation of the free hexosamine with mercuric of relative reactivities of alcohols to fuming oxide gave an acid which had the same melting hydrobromic acid or concentrated hydrochloric point (m. p. 230-232') reported for N-methyl-d- acid a t room temperature. One reactivity seglucosaniic acid.4 Again, the rotation was of the quence obtained in this way is: tmns-2-iodosame magnitude but opposite sign. cyclohexanol 1000; cyclohexanol 1; trans-2Hydrolysis of the product of the reaction be- bromocyclohexanol 0.0s; fm?zs-3-chlorocvclotween I-arabinose, inethylainitle and hydrogen hexanol 1.6 X cyanide 'yave an acid which was identical with the In the relatively reactive substitutcd cyclo"natural" acid described above. IVhen the syn- hexyl compounds (which are typical of most of thetic acid was converted to the lactone, reduced the cases where stereochemical evidence for and acetylated, the product was found to be participation exists) the neighboring group supidentical with the pentaacetyl derivative of the plies a large driving force for the r,ite-detcrmining "natural" hexosamine. Thus, the configurations ionization of the departing group. This parabout C3, C4,and C5of the hexosamine are those a t tially neutralizes or completely overbalances carbons 2, 3, and 4 of 2-arabinose (or carbons 3, 4 (as for I) the rate-retarding intluctive effect. and 5 of I-glucose). The sequence I > Br > C1 is to be expected. A s 11ethyla tion of d-glucosamine, followed by in the case of the acetoxy group, the driving force (1) Brink, Kuehl and Folkers, Sczence, 102, 506 (1945). is supplied from the trans-positiotl and poorly (2) I-Glucose phenylosazone, m p 205O, Fischer, B e y , 23, 374 if a t all from the cis-position. In the case of thc (1890) J O U R V A L , 67. 93" (lQ45) (3) Haskins Hann and Hudson, THIS (4) Votoipk and Luke4. Ciwm L ~ c l v29, 308 (1915)
(1) Winstein and 5cxmour Trrrs J o r r R v i r p r e t i o u q articlrq in t h e ceric,
6 8 , 119 11
