Report of Committee on Nomenclature, Spelling, and Pronunciation

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Report of Committee on Nomenclature, Spelling, and Pronunciation N o m e n c l a t u r e o f the H y d r o g e n Isotopes and T h e i r Compounds N RECOGNITION of the far-reaching significance of the separation in q u a n t i t y of the h y d r o g e n isotope of mass 2 the Committee on Nomenclature, Spelling, and Pronunciation has been devoting considerable time to t h e s t u d y of the interesting a n d important nomenclature problems which this accomplishment has presented. T h e committee has h a d t h e cooperation of representatives of the American Physical Societv appointed for this purpose and has consulted r e p e a t e d l y with a number of chemists and physicists outside the committee who are working in this field (including H . C. Urey). T h e committee h a s also consulted with a like committee of t h e British Chemical Society. A preliminary, unofficial report on the work of t h e committee was published last summer. 1 T h e committee hoped t h a t it might be helpful in guiding usage d u r i n g t h e earlier period of rather feverish activity in this n e w field of research, when confusion in nomenclature was springing u p , b u t felt it desirable to delay definite recommendations for more m a t u r e consideration. T h e committee also wished to gain t h e a d v a n t a g e of suggestions from interested readers. Reference is m a d e to t h i s report for certain details of t h e considerations w h i c h have led t o t h e recommendations now t o be made. In t h e committee's work o n the n o m e n c l a t u r e problems relating t o the hydrogen isotopes, i t has been considered of special importance to keep in mind certain general viewpoints. These take ir+o consideration such m a t t e r s a s (a) the existence of isotopes of m a n y of t h e elements, (b) the fact t h a t t h e isotopes of hydrogen are still forms of hydrogen a n d not new elements, (c) t h e effect of names and symbols o n ease of thinking, (d) t h e teacher's viewpoint, (e) established nomenclature, (/) convenience, a n d (g) indexing (this includes the use of indexes). An effort has been made t o see the picture as c o m p l e t e l y as possible and with the broadest view. Even so it has been considered justifiable t o regard hydrogen as presenting a special case. Convenience seems almost t o require special names and symbols for the h y d r o g e n isotopes or a t least for t h e isotope of mass 2. Hydrogen i s a common element and its compounds are numerous (the w h o l e field of organic chemistry is involved). T h e differences b e t w e e n isotopes of t h e other elements will no d o u b t be slight in comparison. F o r other elements isotopes can be designated b y use of their relatively large mass n u m b e r s in connection w i t h their established names or symbols with less likelihood of confusion t h a n with hydrogen; H 2 and H 2 , for example, might n o t "be clearly differentiated, p a r ticularly when used orally. The committee is of the opinion t h a t u n d e r most circumstances, as in compounds a s a rule, j u s t t h e n a m e hydrogen and its symbol H will serve in place of a special n a m e a n d symbol for t h e isotope of mass 1 as well as for the common mixture of isotopes. A distinguishing adjective m a y be n e e d e d now and t h e n . As one committee m e m b e r p u t it, "the f a c t t h a t classical hydrogen has now been shown t o have been slightly impure should not lead u s to call it an3'"thing b u t hydrogen." I t seems likely t h a t there will be circumstances u n d e r which it will be helpful and in t h e interest of scientific exactness to h a v e a special n a m e and symbol for the hydrogen isotope of mass 1, but i t i s not proposed t h a t the whole of our existing nomenclature for h y d r o g e n and its m a n y compounds shall be revised. One sees -the originally suggested name protium occasionally in t h e literature a n d t h e symbol H 1 seems t o have been appropriately used u n d e r certain special circumstances. T h e committee does n o t object t o the use of protium (it corresponds t o t h e well-established n a m e proton for the nucleus) and of H 1 if need is found f o r special designation at times, but favors, under most circumstances a t least, t h e use of the name hydrogen a n d t h e symbol H for t h e isotope of mass 1. Several names h a v e been proposed for t h e isotope of mass 2. None of these has seemed preferable to the name deuterium proposed by t h e2 discoverers, H . C. U r e y , G . M . M u r p h y , and F . G. Brickwedde. Discoverers have a traditional right t o suggest names, and the careful consideration which preceded t h e exercise of this privilege took into account a n u m b e r of possible names, including diplogen. The name d e u t e r i u m has already come into wide use a n d it seems appropriate t r i â t its use should be continued. T h e n a m e tritium for t h e i s o t o p e of mass 3 is beginning t o appear in t h e literature. It c o r r e s p o n d s with t h e name deuterium. I t s continued use seems desirable. T h e n a m e s hydrogen-p, hydrogen-d, and hydrogen-ί for the isotopes of masses 1, 2, a n d 3 , respectively, have considerable merit in t h e eyes of some who h a v e entered into our discussions. While the committee m a k e s no r e c o m m e n d a t i o n as t o t h e m , it can

I

* Crane, Science, 80, 86-9 (1934). » J. Chem. Physics, 1, 512-13 (1933):

be said t h a t there would probably be nothing objectionable a b o u t their alternate use, a s in teaching, particularly in view of the recommended names for compounds discussed below. D e u t e r o n vs. I > e u t o n T h e name deuton for t h e deuterium nucleus has b e e n objected to by certain scientists in England who believe it t o be easily confused with the name n e u t r o n when used orally. T h i s led to t h e proposal b y Lord Rutherford of the name diplogen for t h e isotope and diplon for its nucleus. I t has been suggested that this difficulty would be o b v i a t e d by the use of the name d e u t e r o n in place of d e u t o n . This is p e r h a p s t h e physicist's field more t h a n t h e chemist's, and in view of action t a k e n at a recent meeting of t h e American Physical Society in a d o p t i n g deuteron your com­ mittee has unanimously voted to fall in line with t h i s action. T h e action b y members of the American Physical Society was reported t o us as follows: A t a symposium o n heavy hydrogen, Dr. Ladenburg proposed during the discussion the use of deuteron instead of deuton or diplon. He reported t h a t this suggestion came from Professor Bohr and that he had brought it back to America via England where he had secured Lord Rutherford's willingness to adopt it. It was reported to the meeting also that the several American schools of nuclear research headed by such men a s Lawrence, Lauritsen, Tuve, etc., were agree­ able to its adoption. Finally, Dr. Urey himself moved t h a t a vote be taken and this vote resulted in approval for deuteron. While this vote was merely an informal consensus of those present and was not taken in accordance with the procedure laid down for recognized votes of the American Physical Society and so cannot be considered an official action of t h a t society, nevertheless, it will be recognized generally and I think you m a y take it for granted that the editors of our publications will hereafter suggest the word deuteron to con­ tributors. Symbols I t is common practice t o use as t h e symbol for a n isotope the element symbol with the mass number added as a right-hand superscript, t h u s CI 37 . T o follow t h e same practice for t h e iso­ topes of hydrogen would, of course, lead to H 2 a n d H 3 for deu­ terium a n d tritium, respectively. These symbols a r e clear and t h e committee is not inclined t o object to their use if a n individual finds this desirable under certain circumstances. T h e y conform well with m o s t of t h e general considerations above mentioned. However, it is desirable for the commoner elements t ο h a v e singlecharacter symbols, a n d t h e symbols D a n d Τ now in considerable use for deuterium a n d tritium, respectively, are a good deal more convenient t h a n a r e H 2 and Η 3 . Η 2 , for example, presents difficulties when used in t h e formulas for compounds. H | 0 , for instance, is a w k w a r d to reproduce orally and it presents t y p i n g a n d printing difficulty. Furthermore the French practice of using superscripts instead of subscripts t o designate t h e n u m b e r of a t o m s in a compound serves as a n objection. Convenience is i m p o r t a n t a n d tends often, to b e a determining factor. I t seems t o have won t h e d a y for D a m o n g deuterium workers, a n d t h e committee, after being divided in opinion for a while, has voted unanimously for D . T h a s been approved with b u t t w o dis­ senting votes. T h e N a m i n g of C o m p o u n d s D e u t e r i u m compounds are being prepared and a n n o u n c e d and t h e n u m b e r of these is likely to be large. These should be n a m e d systematically a n d w i t h d u e attention t o t h e general considerations referred t o in t h e t h i r d paragraph of this report. Some p r e t t y bad names a r e g e t t i n g into print. T h e committee hopes in particular t o help in t h i s phase of development. I n t h e naming of compounds containing one o r more of t h e heavy isotopes of hydrogen t h e compounds can either b e re­ garded (a) a s derivatives of p a r e n t substances in which h y d r o ­ gen has been replaced, in part a t least, b y the isotope or isotopes, or (6) a s compounds of t h e isotope or isotopes, as (a) dideuteriom e t h a n e for CH 2 D 2 and (6) deuterium sulfide for D 2 S. T h e latter practice is satisfactory for a few simple compounds, b u t the former is the m a i n reliance in systematic nomenclature. If applied, however, in t h e manner usually employed in organic chemistry where t h e names of radicals entering a s substituents replacing hydrogen a r e introduced as a p a r t of t h e names of t h e resulting compounds, long a n d sometimes confusing n a m e s result. I t would also result i n the application to inorganic c o m p o u n d s of a typically organic idea. M e t h o d (£>) results in salt-type n a m e s for acids, as deuterium a c e t a t e for C H 3 C 0 2 D . 200

MAY 10, 1935

NEWS EDITION

With the mental attitude that compounds containing D are after all compounds of a form of hydrogen, the committee has sought a system of nomenclature which would result in the least possible change from established nomenclature for hydrogen compounds. Such a system should offer the least obstacle to our mental processes and to effective record-keeping. I t is believed that a system has been found which will accomplish this purpose and which stands the test of general application. This system is a modification of one proposed by Willis A. Boughton. 3 An example of Dr. Boughton's suggestion is the name benzenep2d4 for C6H2D4. This suggestion has been modified by the omission of " p " for most purposes and by the use of italic d, thus benzene-di, and details of application of the system have been worked out (suggestions by Austin M. Patterson, C. D. Hurd, and W. R. Stemen have helped greatly). The " p " can be used if desired in special cases4 so that the method is flexible. The following list of names will serve as further examples of the application of the modified Boughton system. For contrast deuterio names 6 are also given. NH2D ND3 HDSO« Na2SOi.5D20 XHÎDÎOD

NHDOD CH3D CD* CDCh CHjDC(CHi CHaCDO CDaCDO

Boughton Names ammonia-d ammonia-ck sulfuric acid-rfî sulfuric acid-d sodium sulfate pentahydrate-djo or penta-(hydrate-ck) ammonium-dî hydroxide-d hydroxylamine-ûr,/S-c?2 or hydroxyl-cfamine-dt methane-d methane-d·» chloroform-cf 2,2-dimethylpropane1-d or neopentane-c? acetaldehyde-ii acet-d3-aldehyde-d

CH 3 CH 2 OD

ethyl alcohol-d

CH3CH2COOD

propionic acid-d propionic-/5-d acid-d

CHÎDCHSCOOD CHJDCONHD

acetamide-iV.ar-ek or aoet-d-amide-d benzene-de chlorobenzene-2,3-d2

Deuterio Names deuterioammonia trideuterioammonia sulfuric dideuterioacid sulfuric deuterioacid or sulfuric monodeuterioacid sodium sulfate pentadideuteriohydrate dideuterioammonium deuterioxide ex,β - dideu ceriohydroxylamine or deuterioxyldeuterioamine deuteriomethane tetradeuteriomethane deuteriochloroform 1-deuterio - 2,2 - dimethylpropane or deuterioneopentane acetodeuterialdehyde t r i d e u t e r i o a c e t o deuterioaldehyde O-deuterioethyl alcohol or ethyl deuterioalcohol propionic deuterioacid β - deuteriopropionic deu­ terioacid N, ot-dideuterioacetamide

pben-4-d-ol-d benzoic acid-d benzoic-2,4-da acid

hexadeuteriobenzene 1 - chloro - 2,3 - dideuteriobenzene «,3-dideuteriotoluene O-deuteriophenol or benzenedeuteriol 0,4-dideuteriophenol benzoic deuterioacid 2,4 - dideuteriobenzoic acid

DHNO:CD.CH:CH.CH:OH

aniline- N,2-dz

iV,2-dideuterioaniline

HOOC(!;:C(COOD).-

phthalic-4-d acid-2-d

4 - deuteriophthalic terioacid

CeDe

2 f 3-D 2 C6H 3 Cl 3-DC6HiCH 2 D CeHsOD 4-DC 6 H 4 OD C»H s COOD 2,4-D2C 6 H 3 COOH

CH:CD.CH:OH

toluene-ot,3-d2 phenol-d

this, however, in the naming of chemical compounds. Another objection is the fact that ρ and d are in use in organic chemistry to designate para and dextro, respectively. However, ρ for para can be avoided by the use of numbers and it is suggested that in the rare instance in which the dextro difficulty might arise the word "dextro'' should be spelled out. The use of the d after names instead of before them will help in keeping this sort of thing clear also. The Boughton system of naming grows in favor as one experi­ ments with it. The committee's experimentation with this system and with other possible naming methods was carried rather far. Compounds chosen to be representative of all of the different types of possible difficulties which came to mind were named and set up in type. Name lists were distributed among a considerable number of interested chemists and physicists. The Boughton names stood the test of this experimentation and met with almost universal approval. They have the rather en­ thusiastic support of members of the committee. Dr. Urey's comment has been, "I like the Boughton names very much and I am going to use them." He is doing so.6 The Boughton names were adopted for use in the 1934 Subject Index to Chemical Abstracts. They have served very well for indexing purposes. The Boughton system apparently leads to the least possible change in established names for hydrogen compounds, which is a consideration of fundamental importance. If compounds of tritium are eventually made they can readily be named in like manner, t being used as is d in the Boughton names for deuterium compounds. Opinion in the committee with reference to such expressions as "heavy water," "heavy ammonia," etc., is that this use of "heavy" is justified no matter what heavy isotope may be represented, whether it be an isotope of hydrogen or of another element, and that such expressions, though not scientific, are handy for use in a generic sense. Your committee is a large one (20 members). In spite of this fact only three dissenting votes (each with reference to a single minor item) were received in connection with the whole series of recommendations in this report. The cooperating physicists have given full approval. Pronunciation Report The committee's report on the pronunciation of chemical words, made last year, has apparently aroused much interest, particularly among teachers. Hardly a dry passes without the receipt of requests for reprints of the report with its rather ex­ tensive word list. A big supply was obtained and copies are still to be had. A charge of five cents each, to cover mailing cost, is made for them. E. J. CRANE, Chairman

β

2-deu-

With reference back to the lettered general considerations given in the third paragraph it will be noted that the Boughton names conform with (b), (c), (d), (e), (/), and (g). It will also be noted that the other system results in many strange names which, as Dr. Patterson has stated, will have to be deciphered "to find the compounds old friends in disguise." A flood of deuterio names, some of which would be confusing, would be a real handicap in organic chemistry. Owing to the complexity of many organic compounds, organic nomenclature is already complicated and difficult and it seems very important to do everything possible to simplify the further complications presented by the far-reaching new possibilities opened up by the separation of deuterium. An advantage of the Boughton names is their brevity. Con­ trast, for example, aeetic-