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Recent Chemical Studies of Sodium Nitroprusside pressure as required. A major advantage of sodium nitroprusside over many other hypotensive drugs is that on adjustment of the dose-rate there is very fast response, without overshoot. It has also been used, in a similar manner, in the treatment of chronic hypertension and in the management of myocardial infarction and other cardiac failure conditions.' '--Sodium nitroprusside is thus an effective drug for the treatment of two conditions, high blood pressure and heart attack, which are extremely common and wide-spread. However, its usage has been severely restricted by reports l4-I9 that, in the bloodstream after infusion, nitroprusside decomposes with liberation of most or all of the cyano ligands as free cyanide. In a number of cases administration of sodium nitroprusside has been followed by the symptoms of apparent cyanide poisoning. Several deaths following surgery have been attributed to 3 The Problem of in vitvo and in vivo Cyanide Release Although there are many reports in the medical 1iteratu1-e~~ which claim to demonstrate the ready liberation of four or five moles of free cyanide per mole of nitroprusside, very few, if any, of its chemical reactions 3.4 liberate any free cyanide. Indeed, the very high formation constants of cyanoferrate complexes { p6 e for [Fe(CN),I4-and 2:for [Fe(CN),I3-} 24 suggest that loss of C N -is very unlikely unless some other powerful driving force for the reaction is provided. One such is protonation of CN-to give HCN, which should occur at physiological pH, since pK, for HCN is 9.21. On the other hand, [Fe(CN),NOl2-is substitutioninert, and exchanges its cyanide ligands with [14CN] -extremely slowly (tt -1000 h even at pH 2.3).25 Hence, the widely reported rapid liberation of cyanide from nitroprusside in uiuo immediately poses problems to the inorganic chemist.An essential prerequisite of any study, whether in uiuo or in uitro, of cyanide release from sodium nitroprusside is an analytical technique which will distinguish reliably between free cyanide and bound cyanide. The most widely employed method for the analysis of cyanide in biological samples is that of Boxer and Rickards: 2 6 the sample is acidified (eg. with sulphuric or trichloroacetic acid) and the resulting HCN removed on a stream of nitrogen gas from which it is trapped by "

In the P polymorph of benzanilide or N‐phenyl­benz­amide, C13H11NO, the mol­ecules are linked into simple C(4) chains by N—H⋯O hydrogen bonds. The mol­ecules exhibit orientational disorder, but the donor and acceptor in a given hydrogen bond may occur, independently, in either the major or the minor orientation, such that all four possible N—H⋯O combinations have very similar geometries. The structure of this P polymorph can be related to that of a previously reported C2/c polymorph.

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The structures of eight 2,4,6-trisubstituted-5-nitrosopyrimidines (one of which crystallizes in two polymorphs) have been determined, including seven O6-benzyl derivatives which are potential, or proven, in vitro inhibitors of the human DNA-repair protein O6-alkylguanine-DNA-transferase. In the derivatives having an amino substituent at the 4-position, an intramolecular N—H...O hydrogen bond with the nitroso O as an acceptor leads to an overall molecular shape similar to that of substituted purines. There is a marked propensity for these nitroso compounds to crystallize with Z′ = 2. The structure of an analogue with no nitroso group is also reported for comparative purposes. Compounds containing the N-alkyl substituents —NHCH2COOEt, —NHCH2CH2COOEt and —NHCH(CH2Ph)COOEt, derived from amino acid esters, exhibit a rich variety of conformational behaviour, and in all of the nitroso compounds the bond lengths provide strong evidence for a highly polarized electronic structure. Associated with this polarization is extensive charge-assisted hydrogen bonding between the molecules, leading to supramolecular aggregation in the form of finite (zero-dimensional) aggregates, chains, molecular ladders, sheets and frameworks.