Reaction Gives gem-Dinitro Compounds Technique offers way to make sensitive and hindered derivatives under mild conditions A simple, general reaction puts two nitro groups on the same carbon atom. Silver nitrate and inorganic nitrates react with salts of primary and sec ondary nitro compounds to form gemdinitro compounds. The technique was worked out by Dr. Harold Shechter and Dr. Ralph B. Kaplan (now at DuPont) at Ohio State University. It was unveiled at a Purdue symposium on nitroaliphatic chemistry, sponsored jointly by Purdue and the Office of Naval Research. The find means that chemists can make primary, secondary, and func tionally substituted gera-dinitro com pounds under mild conditions. And they can synthesize sensitive and hindered derivatives that can't be made by other methods. Dr. Shechter and Dr. Kaplan de veloped the synthesis to fill the need for a more efficient way to form gemdinitro compounds. Until now, the practical methods that were available have been limited to making very few compounds. General methods avail able are so inefficient, they are useless and a real bottleneck to advances in the field, the two chemists say. Mechanism. In the new reaction, an addition compound forms first, then decomposes into the gem-dinitro com
pound and silver, Dr. Shechter says. The reaction temperature can be be low 30° C. and the reaction is only slightly exothermic. It goes in neutral or aqueous alkaline media with yields ranging from 60 to 9 5 % . Most of the reactions are complete within five min utes. Silver can be recovered quan titatively as the nitrate, Dr. Shechter adds. Dinitromethane, among others, has been made directly from this reaction. Dr. Shechter says. But the direct method isn't as practical (yields are too low) as first making 2,2-dinitro-l, 3-propanediol using the silver nitrateinorganic nitrate on a salt of 2-nitro-l, 3-propanediol, then hydrolyzing it with alkali. This forms the dinitro methane and water; variations in this system can produce 1,1,3,3-tetranitropropane. The reaction can also be used to make sensitive and hindered deriva tives such as 3,3-dinitro-2-butanol and 2,2-dimethyl-l,l,3-trinitiOpropane, which can't be made by other meth ods. Arylalkanenitronates will react with the silver and nitrite ions to form gem-dinitro compounds along with carbonyl derivatives and vicinal-dinitio compounds. Phenylnitromethane, for instance, yields phenyldinitromethane,
Addition Compound Forms First 1
ν
Nitronate
Intermediate complex salt; second nitro group is introduced here Then Decomposes to Product
^ ^ C
/
Φ
\
ί
Λ +A
g
gem-Dinitro compound 44
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benzaldehyde, and meso- and d,l-l,2dinitro-1,2-diphenylethane. Dr. Shechter and Dr. Kaplan checked a number of other cationic oxidizing agents but found none as effective as silver. Mercuric nitrate works but it's an acidic reagent, works slower than silver. Also, results aren't reproducible and yields are low. Other cationic oxidants are poor. Cupric ammonium hydroxide forms only vicinal-ainitw compounds by oxida tive dimerization; cuprous chloride, cu prous acetate, ammoniacal cuprous chloride, and Fehling's solution form aldehydes and ketones. Anionic ma terials such as sodium persulfate and sodium peroxide give vicinal-aimtro compounds and carbonyl derivatives. Neutral potassium permanganate gives carbonyl compounds only.
New Coding Theory May Aid Study of Protein Synthesis A new biological "code" for protein synthesis has been proposed by Dr. Carl Woese of General Electric's re search laboratory, Schenectady, N.Y. The code, GE says, fits practically all the data that are available on pro tein structures and seems to approxi mate the true code. Dr. Woese's theory, as are other coding theories, is based on the order of nucleotides in ribonucleic acid (RNA). A number of possible ways that RNA's four nucleotides might be arranged have been suggested in the past. Most of these proposed com binations treat the four nucleotides in groups of three; each group of three nucleotides corresponds to one amino acid. The code for nucleotides 1, 2, 3, and 4 would consist of combinations like 123, 431, 224, and so on. Dr. Woese developed his code by making the combinations fit the pro portions of amino acids known to exist in some viruses. He arranges the order of nucleotides—for example, as 123 instead of 312 or 132-so that the fewest changes can explain the dif ferences between nearly identical pro teins, which differ from each other in only a few of their amino acids. Slight differences in protein are caused by mutations in the RNA that's involved; these are rare, he adds. Thus, the smallest possible change in the code seems to be the most likely one, he explains. Until more protein structures are known, however, Dr. Woese's code will remain an approximation.
