body's burden of lead is concentrated in the bones; the substance is readily mobilized, however, during periods of high-calcium metabolism, such as during feverish illness. Relatively little lead transferred to the soft tissues, notably to the brain and nervous system, the blood, and the kidneys, can produce severe or even fatal damage. Children in the under-five age bracket are especially susceptible. Acute poisoning by lead is rather easily recognized by physicians. The more common chronic cases, however, can be marked by vague symptoms easily confused with common lethargy, learning difficulties, or simple nervous disorders. Vagueness, however, does not imply insignificance. The matter of lead-painted pencils is a most serious one. Anyone with even a casual familiarity with the classroom can attest to the high incidence of pencil chewing among young children. An official of HEW'S Maternal and Child Health Services has stated that children three years of age or under should ingest no more than 300 pg of lead per day. (The air we breathe and the food we eat contribute to this daily total.) A child eating just one milligram of paint, an amount equal in weight to about one thousandth of an aspirin tablet, would receive 300 pg, if the paint contained 30% lead. Further information concerning the basic medical and environmental aspects of lead poisoning may be found in the current issue of Environmental Science and Technology in an article by Stephen K. Hall.
Divalent sulfur can also react as a soft Lewis acid and as a general Usanovic acid allowing it to be readily reacted with bases of many sorts. The reactions of thiocompounds with hydrides, trivalent phosphorus compounds, and Raney nickel are examples in this category. One important synthetic example not mentioned by Block is the conversion of oxathiolanes to carbonyl compounds by Raney nickel. The availability of d orbitals for reaction can be used to rationalize not only octet expansion reactions but also the stability of anions alpha to sulfur and reactions which probably proceed through triplct states such as the dimerization of thiophosgene and other thiocarbonyl compounds to 1,3-dithiacyclobutanes, other irradiation promoted reactions and the easy oxidation by molecular oxygen of many sulfur compounds. The possible application of thiocompounds in any synthesis deserves serious consideration as these compounds have acid base characteristics markedly different from their oxygen analogs, as well as octet expansion capabilities and relatively low-lying triplet states which allow redox reactions to take place which are impossible with the 0x0-analogs. Two almost unknown publications which might be of value to other workers in the area of organic sulfur chemistry are 0. C. Dermer, "Copolymers of Olefin Sulfides," W.A.D.C. Technical Report, 55-447, Wright Air Development Center, June 1956, which contains information on oxathiolanes which is otherwise unavailable; and a dissertation, "Thermal Decomposition of 1,3-Dioxan-2-ones and 1,3-Dioxan-2-thiones with Comments on the Structure of the Thiocarbonyl Group," Microfilm Abstracts Order No. 67-9151, 158 pp., $7.40 by Xerography, which contains infrared and pmr data and synthetic methods for thiocarbonyl compounds which are not available elsewhere.
Organic Sulfur Compounds in Synthesis
To the Editor: The excellent review by Eric Block on "Organic Sulfur Compounds in Organic Synthesis" [J.CHEM.EDUC., 48, 815 (1971)], does not explicitly state some broad summary generalizations which are useful in considering the use of organic sulfur compounds in synthetic work. These particular generalizations complement rather than contradict Block's discussion. Divalent sulfur is an excellent nucleophile in displacement reactions and a soft base which reacts readily with soft acids such as heavy metal cations and positive halogen compounds, while reacting much less readily, if at all, with relatively hard acids such as boron trifluoride. Two reactions which deserve to be better known illustrate these ideas. One is the reaction of mercaptans, mercaptide salts, and carbon tetrachloride to form disulfides and trithioformates. RSH
+ 4RSNa + CC4
+ RSSR
+ HC(SR), + 4NaCI
This reaction probably has as one transient intermediate an analog of C1,-. The reaction of thiqacids, boron trifluoride, and nmercaptans to form dithioesters is predicated specifically on the great difference in reactivity and bond stability of divalent oxygen and divalent sulfur with respect to boron trifluoride. An example is 380
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Journal of Chemical Education
DEANL. SINCLAIR
Scientitlc Writing Course Survey
To the Editor: The Council of Biology Editors (CBE) has long sought to improve the quality of scientific writing, especially in professional journals. Now, through its Committee on Training in Scientific Writing, CBE is attempting to identify all those governmental and industrial institutions that offer to their scientists formal courses in scientificwriting. A s a related matter, CBE would like to know of courses in scientific writing that are being taught in undergraduate, graduate, and professional schools.
