Metals picrates

In Pedersen s early experiments, the relative binding of cations by crown ethers was assessed by extraction of alkali metal picrates into an organic phase. In these experiments, the crown ether served to draw into the organic phase a colored molecule which was ordinarily insoluble in this medium. An extension and elaboration of this notion has been developed by Dix and Vdgtle and Nakamura, Takagi, and Ueno In efforts by both of these groups, crown ether molecules were appended to chromophoric or colored residues. Ion-selective extraction and interaction with the crown and/or chromophore could produce changes in the absorption spectrum. Examples of molecules so constructed are illustrated below as 7 7 and 18 from refs. 32 and 131, respectively. 

Calestani et al. [8] prepared dietylamide of the tetra-carboxymethyl ether of p-tert-h W.y calix[4]arene and reported alkali metal picrate extraction constants of 1.9... 

The fact that all ligands failed to transfer Fe " ion from the aqueous into the organic phase was not unexpected, since this ion prefers to bind with picric acid more than the other ligands. This property is typical only for the Fe " ion [54]. Yet, our previous observations [49] indicated that, when FelNO.ala was used instead of metal picrate, it was possible to efficiently extract Fe " into the organic phase by utilizing ligands 1, 3, and 4. 

Table 5 Extraction of Metal Picrates with Ligands ...

Although metallic picrates have been known since as early as 1795 (Ref 4), there is still much confusion in regard to their compn and properties. The first application of picrates as exp Is seems to have been made in 1869 by Designolle of Fr, who proposed the use of K picrate, K nitrate and charcoal in various proportions. Fontaine proposed a mixt cf K picrate and K chlorate, while Brugere and Abel, independently, and about the ame time (1869), proposed the use of mixts of Amm Picrate and K nitrate (Ref 7)... 

The first systematic study of metallic picrates seems to have been done in 1901 by Dupre... 

Ref 2). This was followed by Will in 1906 (Ref 3), Silberrad and Phillips in 1908 (Ref 4), and Kast in 1911 (Ref 5). More recently (1938), Hopper of PicArsn (Ref 6) detd and described the expl properties of the following metallic picrates Ai, Cd, Cr, Cu, Fe+3, Fe+2, Na, Ni and Zn. In general,he prepd the salts as cryst hydrates from aq solns by methods outlined by Silberrad Phillips, and Kast. These were then dehydrated by heating at temps of 80 to 150°, depending on the ease with which the w of crystn could be driven off, to obtain the desired degree of hydration... 

According to Hopper, the relative sensitivity of metallic picrates depends largely upon the amts of w of crystn present. The highly hydrated forms are wry insensitive, the lower hydrates are in general more sensitive, and the anhydr forms most sensitive. The anhydr salts, with the exception of Na, Amm, Al and Fe+2, are more sensitive to impact than PA. Anhydr Cu, Zn and Cd picrates are only slightly more sensitiw, while anhydr Ni picrate is especially sensitive, lying in the sensitivity range between MF and Tetryl... 

JFranklnst 225, 219 (1938) (Explosive characteristics of certain metallic picrates)... 

If, however, the material is concentrated in a small area or when it is in a confined space, explosion may occur. Burning Picric Acid containing metal picrates may result in explosion. Similarly a potential danger exists when burning Picric Acid is in contact i ith metals, since in the molten state it forms picrates which may initiate explosion. This depends largely on the metal lead, iron, copper should be considered particularly dangerous ... 

Picric acid, in common with several other polynitrophenols, is an explosive material in its own right and is usually stored as a water-wet paste. Several dust explosions of dry material have been reported [1]. It forms salts with many metals, some of which (lead, mercury, copper or zinc) are rather sensitive to heat, friction or impact. The salts with ammonia and amines, and the molecular complexes with aromatic hydrocarbons, etc. are, in general, not so sensitive [2], Contact of picric acid with concrete floors may form the friction-sensitive calcium salt [3], Contact of molten picric acid with metallic zinc or lead forms the metal picrates which can detonate the acid. Picrates of lead, iron, zinc, nickel, copper, etc. should be considered dangerously sensitive. Dry picric acid has little effect on these metals at ambient temperature. Picric acid of sufficient purity is of the same order of stability as TNT, and is not considered unduly hazardous in regard to sensitivity [4], Details of handling and disposal procedures have been collected and summarised [5],... 

A small sample, isolated incidentally during decomposition of a picrate with ammonia, exploded dining analytical combustion. The presence of traces of metallic picrates (arising from metal contact) increases heat sensitivity. The salt may also explode on impact. 

Table 1. Extraction (%) of alkali metal picrates from the aqueous into the organic phase by 3a-d 3a-d 10 2 M (in dichloromethane), alkaline metal picrates 10 1 M (in water), picric acid 7xl0 5 M (in water).

MCAm is the ion-pair formed between the crown (C) complex containing the metal ion (Mm+) and A- is the counter ion. It needs to be noted that the degree of extraction is anion-dependent. For example, the extraction of an alkali metal into an organic phase is enhanced when the counter ion is a large anion such as picrate. Alkali metal picrates undergo extraction into benzene in the presence of 18-crown-6 in the order K+ > Rb+ > Cs+ > Na+ (Iwachido, Sadakane Toei, 1978). Divalent ions may also be extracted. For 15-crown-5 in benzene, the picrate extraction coefficients (from water) fall in the order Pb2+ > Sr2+ > Ba2+ > Ca2+... 

Kollig, H.P., Ellington, J.J., Weber, E.J., and Wolfe, N.L. Environmental research brief - Pathway analysis of chemical hydrolysis for 14 RCRA chemicals. Office of Research and Development. U.S. EPA Report 600/M-89/009, 1990, 6 p. Kolthoff, I.M. and Chantooni, M.K., Jr. Crown ether complexed alkali metal picrate ion pairs in water-saturated dichloro-methane as studied by electrolytic conductance and by partitioning into water. Effect of lithium chloride on partitioning, J. Chem. Eng. Data, 42(l) 49-53, 1997. 

In the tetra-bridged phosphocavitands containing four donor P(0)R groups, the P=0 bonds can adopt the inward (f) or outward (o) orientations relatively to the molecular cavity. Only the ini isomer with the four P=0 groups oriented inwards can benefit from both cooperativity of P=0 binding and r-in-teractions with the aromatic cavity of the resorc[4]arene framework [19, 63]. The complexation properties of new iiii tetra-phosphonatocavitands 12b-12d and 12g towards metal ions were characterized by extraction of the metal picrate from water to chloroform solution containing the host compound (Fig. 4). 

Fig. 4 % Extraction of metal picrates by phosphorylated cavitands 12b, 12c, 12d, and 12g (extraction of Ag(I) with 12b was not measured)...

Trinitrophenol (4), commonly known as picric acid (VOD 7350 m/s, d = 1.71 g/cm ), was once used as a military explosive although its highly acidic nature enables it to readily corrode metals. This kind of reaction has led to many fatal accidents, a consequence of some metal picrates being very sensitive primary explosives. The lead salt of picric acid is a dangerous explosive and should be avoided at all cost. In contrast, the ammonium (Explosive D, VOD 7050 m/s, d = 1.60 g/cm ) and guanidine salts of picric acid are unusually insensitive to impact and have been used in armour piercing munitions. 

Although the thermodynamic data reported for the solvent extraction equilibria are limited, we obtained a well-correlated AH-TAS compensation plot (Figure 22) for the solvent extraction of aqueous metal picrates with crown ethers in organic solvents. Quite interestingly, the slope (a 0.73) and the intercept (TASq 2.6) are very... 

Table 7. Photostationary cis/trans Percentages and Extractabilities of Alkali Metal Picrates with lonophores 88, 89, and 90 under Visible and UV Light Irradiation ...

Agrawal, J.P. (1970) Ph.D. Thesis entitled, Explosive Nature of Metal Picrates and Picramates, Gorakhpur University. 

A plot of logio Ed against 1/1) is almost rectilinear. Therefore, Ea may be determined by equating (EJ4.57) with the slope of the straight line. Equation 3.3 holds good for a number of explosives such as lead azide, cuprous azide, mercury fulminate, lead styphnate, barium styphnate and metal picrates and metal picramates etc. [25-30]. Thus, it appears that the determination of Ea gives a more complete picture concerning the heat sensitivity of explosives than ED or ET. 

In 1861 Designolle [33] suggested using potassium nitrate mixed with metal picrates, mainly potassium picrate, as a propellant substitute for ordinary black-... 

Disc kerb off Powders. Mixtures of BkPdr with at least 15% of one/or several alkali metal picrates. The BkPdr could be substituted by a mixture of K nitrate and sulfur Ref Daniel (1902), 205... 

Many polypodands having terminal donor groups are also available, e.g. (39)-(41).33 These also exhibit cation complexation and phase transfer properties. KMn04 and aqueous alkali metal picrates are much more readily taken into organic phases in the presence of these podands than with dibenzo-18-crown-6.239 The KSCN complex of (39) exhibits a novel coordination geometry as all 10 donor atoms participate in coordination of the metal cation, and in order to do this the three arms wrap around the cation in a propeller-like fashion.240... 

More recent studies show some variations to the above generalities. 13C and 23Na NMR studies indicate that for Na+ the complexation sequence is 18-crown-6 > 15-crown-5 > benzo-lS-crown-5,482 hinting at the need for ligand flexibility conduction data reveal that for 18-crown-6 the stability sequence is K+>Rb+>Cs+>Na+ 483 extraction studies using metal picrates show that for benzo-15-crown-5, Na+ > K+ > Rb+ > Li+ > Cs+ for 1 1 complexes and that for the corresponding 1 2 complexes K+ > Rb+ > Cs+ 484 further extraction work indicated... 

Selectivity sequences in solvents such as water, methanol and ethanol do not guarantee a similar behaviour in the lipid membrane. Experiments have been carried out in attempts to investigate the selective transfer of cations across model membranes, and these are exemplified here by reference to an investigation concerning the cryptands [2.2.2], [3.2.2], [3.3.3] and [2.2.C8]. Two aqueous phases (IN and OUT) were bridged by a chloroform layer into which the carrier can be dissolved. Alkali metal picrate was dissolved in two aqueous layers such that the IN layer was 1000 times more concentrated than the OUT layer. All layers were stirred and the transport monitored via increase in picrate in the OUT layer (UV) and increase in potassium in the OUT layer (atomic absorption). The membrane phase was also analyzed at the end of the experiment.497... 

Polynitro compounds, e.g. picric acid (and heavy metal picrates), trinitrobenzene (TNB), trinitrotoluene (TNT) all these substances are safe when damp with water. 

The distribution (or partition) coefficient, Ka, of a metal cation between an aqueous (aq) and organic (org) phase may also be used to assess the selectivity of a given host for a range of metal cations under standard conditions, using the equilibrium constants (K) for the following processes (Equations 1.17-1.20) (for metal picrate (Pic) salt, water (aq) and water-saturated chloroform (org) phases, 25 °C). 

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