Hydrogen sulfide, displacement

In this case, the weak, volatile acid hydrogen sulfide displaces the strong, low volatile sulfuric acid from its salt. 

In the dual-temperature H2O/H2S process (61,62), exchange of deuterium between H20(l) and H2S(g) is carried out at pressures of ca 2 MPa (20 atm). At elevated temperatures deuterium tends to displace hydrogen in the hydrogen sulfide and thus concentrates in the gas. At lower temperatures the driving force is reversed and the deuterium concentrates in H2S in contact with water on the tiquid phase. 

Vapor Density (VD) — the mass per unit volume of a given vapor/gas relative to that of air. Thus, acetaldehyde with a vapor density of 1.5 is heavier than air and will accumulate in low spots, while acetylene with a vapor density of 0.9 is lighter than air and will rise and disperse. Heavy vapors present a particular hazard because of the way they accumulate if toxic they may poison workers if nontoxic they may displace air and cause suffocation by oxygen deficiency if flammable, once presented with an ignition source, they represent a fire or explosion hazard. Gases heavier than air include carbon dioxide, chlorine, hydrogen sulfide, and sulfur dioxide. 

It is interesting to note that Kulstad and Malmsten have utilized yet another method for introducing nitrogen into the crown precursors. They utilize sodium azide in DMSO to displace halogen from triethylene glycol dichloride. The bis-azide is then reduced using hydrogen sulfide in ethanol. ... 

Ceftiofur (57) differs from the preceding cephalosporin derivatives in that it ha.s a thioester moiety at C-3. This can be introduced by displacement of the C-3 acetyl group of 7-aminocepha-losporanic acid (40) with hydrogen sulfide and esterification with 2-furylcarboxylic acid to give synthon 5reacted with trimethylsilylated oximinoether derivative 55 (itself obtained from the corresponding acid by reaction with dicyclohexylcarbodiimide and 1-hydroxy-benzotriazole) to produce, after deprotecting, ceftiofur (57) [18]. 

Hydrogen sulfide is undesirable because its presence can lead to the formation of potassium p-toluenesulfinate. The latter can be formed by the desulfurization of thiotosylate by hydrogen sulfide generated in the reaction of potassium hydrosulfide with tosyl chloride. Attention should be directed toward control of the reaction temperature so that hydrogen sulfide is rapidly removed, thereby ensuing survival of the S—S bond of the thiotosylate. p-Toluenesulfinate ion can displace bromide to form stable sulfones which are less soluble in common solvents, such as benzene, than trimethylene dithiotosylate. Therefore, purification of the dithiotosylate contaminated with the sulfones is difficult to achieve by means of fractional recrystallization. 

FIGURE 6.21 (A) Removal of trityl and acetamidomethyl from sulfhydryl by oxidative cleavage by iodine. (B) Cleavage of terf-butylsulfanyl by mercury(II) acetate,88 followed by displacement of the metal ion by hydrogen sulfide. 

A halogen directly attached to the 1,2,4-triazine ring is very reactive and can be replaced by most other nucleophiles as outlined in Scheme 9. Tlie reactivity toward neutral nucleophiles decreases from the 5-position to the 3- and 6-positions, while that towards anionic nucleophiles decreases from the 5-position to the 6- and 3-positions. Among nucleophiles which displace halogen atoms are water, alcohols, amines, hydrazine, hydroxyl-amine, thiols and hydrogen sulfide. It is also reported that the bromine in 6-bromo-1,2,4-triazine-3,5-dione can be replaced by fluorine (323) or by a cyano group (324). 

Multiple 5-10-m-thick cold water intrusions were notable over a 150-m-thick (15.20-16.70 kgnr3) layer. This interleaving led to intensification of interactions between oxic and anoxic waters, which is clearly seen in the distributions of all the parameters studied (Fig. 7). This interaction especially resulted in an increase in the concentrations of Fe(III) and particulate manganese. At this station the hydrogen sulfide boundary was displaced down to a deeper position at 16.40-16.50 kg nr3 (180-200 m). Basturk et al. [38] observed similar displacement to the same density level in the region of the Sakarya, which is east of this location. 

The sulfonation reaction is reversible and benzenesulfonic acid may be desulfonated by treatment with dilute acid at 150 °C. The group can be displaced by fusion of its salt with sodamide to give the corresponding amine, with sodium hydroxide to give the phenol, sodium cyanide to give the nitrile, and potassium hydrogen sulfide to give the benzenethiol (Scheme 5.10). 

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