Historical Inaccuracies To the Editor: In his essay on "The Early History of Spectroscopy", Thomas ( I ) writes: For example, in 1885,J. J. Balmer observed the spectrum of hydrogen, the lightest element, which showed the simplest nsible line spectrum with emission wavelengths 6563,4861, 4341,4102,and 3910 A. This off-hand remark cannot but mislead the uninformed reader into believing that Balmer actually observed the spectrum of hydrogen in 1885. As it happens, Balmer was not a spectroscopistand, so far as one can tell, never observed any spectral lines. We can safely assert that 1885 is the vear in which Balmer announced his breathtaking formka, having deduced it by using, in the words of Pais (2a). "nothing more, nothing less than kgstriim7sdata" about the fo;r hydrogen lines known as &,Hp,H,and &.These four are usually called the visible Balmer lines; the H,line at 3970 A was presumably too weak and too far in the violet to be seen by the careful Angstrom. In the section entitled The Development of Mass Spectrometry, the author states: '.Secondly, Thomson experimentally proved the existence of isotopes, which hitherto had been nostulated bv Frederick Soddv in 1913." This re- ~ - r~~~~ mark, a real mix up, is historically inaccurate and syntactically incondite. The grammar could be repaired-if one were willing to rewrite history-by replacing the subordinate clause by "which had remained unobserved since being postulated by Soddy in 1913", or something similar. However, the author refers the reader to Thomson's book, which appeared in 1913; what is one to make of the adverb hitherto even if one is prepared to put up with a grammatical monstrosity? ~ c t u d l iSoddy , did n i t merelypostulate the existence of isotooes: he discovered them in the course of his work on the rabioactive elements. Though the term isotope was used in print (by Soddy) in 1913, the occurrence of isotopes of radioactive elements had already been established by Soddy in 1911; he also emphasized, in 1911, that the "recognition that elements of different atomic weights may possess identical chemical properties seems destined to have its most important applications in the region of inactive elements" (2b, 3).To J. J. Thomson belongs the credit of finding, before anyone else, evidence for the occurrence of inactive isotopes, Ne2' and NeZ2;he was, however. reluctant to admit the existence of two forms of neon with different atomic weights, and it was Soddy, not Thomson, who made the correct identification. References to the original sources and other essential details have been cornoiled with meticulous care bv Pais (2) and Kauffman (3). I am a little surprised that, though he discusses nuclear magnetic resonance spectroscopy(NMR), Thomas does not mention-not even in passing+lectron spin resonance spectroscopy (ESR).Had he included ESR in his survey, he could have used the o~oortunitvto mention a very interesting development: {he beliefthat isoptopes cannot be separated chemicallv has now become untenable--at least for isotopes of carbon and oxygen. The interaction, within a radical, between the spin of an unpaired electron and the magnetic moment of a C13nucleus or an 0" nucleus affects the rates of chemical reactions between radical pairs and ~
~
has opened up the possibility of chemical separation of isotopes through a process sensitive to nuclear spins rather than nuclear masses (4). Literature Cited 3. ~sukman, G. 8. J then Educ. 198Z, 59.3. 4. ~ a y a s hH, i mametic meld Effects on ~ p a m i Behadour e and ChemicalReactims
ofEvitedMo1des";Vol. 1inPhotochPmistryodPhoffphy9ier;RabekJ. F.,Ed.; CRC. Boea Raton. F L 1990:PO 111-9.
K. Razl Naavi Department of ~hysi'cs University of Trondheim N-7055 Dragvoll, Norway
A Puzzle within a Puzzle To the Editor: We have conducted "APuzzle-SolvingExperiment Utilizing a Grignard Reagent" by Silversmith [J. Chem. Edw. 1991, 68,6881 and would like to point out a change that should be made in order to obtain the desired results. When we reacted chalcone and phenyl magnesium bromide in a 1:l molar ratio, the major product was 1,2,2triphenyl-l-propanone, 3, not 1,2,5-triphenyl-2-(diphenylmethyl)-1,5-pentanedione,5. We obtained 5 in only 7% vield. not the 42% vield claimed in the article. It turns out ihat /fa 1:l ratlo i&sed the amount of5 produced depends on how fast the chalcone solution is added. It stands to reason that ifone wants the cnolate resulting from initial 1,4addltion to react with a molecule of chalcone to produce 5, then a Grignard reagenuchalcone ratio of 1:2should be used instead of a 1:l ratio. By using a 1:2 ratio, we obtained an 80% yield of 5. As an extension of the experiment, the product 3 can subsequently be reacted with one equivalent of phenyl magnesium bromide to produce the 1,1,3,3-tetraphenyl-lpmpanol, 4, mentioned by Silversmith as being available from chalcone but only if a 14-foldexcess of phenyl magnesium bromide is used. Josef G. Krause Niagara University Niagara University, NY 14109
To the Editor: I am grateful to Professor Krause for the improvements solutions he has suggested. We added the chalcon-ther to the Grignard solutions a t a rate of about 2 mumin. Krause's idea of using a 1:2 Grignard reagentkhalcone ratio is excellent; his method doubles the yield of 1,3,5triphenyl-2-diphenylmethy1)-1.5-pentanedione,and it removes all worry about the addition rate. His fmding that 1,2,2-triphenyl-l-propanone reads with one equivalent of phenylmagnesium bromide to produce 1,1,3,3tetraohenvl-l-~ro~anol can provide students with vet another'cha5enG. By the way, the -CH(OH)Ph groups in structures 2 and 4 of the paper should be changed to -C(OH)Phz. Ernest F. Silversmith Morgan State University Baltimore, MD 21239 &
Volume 70 Number 7 July 1993
605
