Direct action

Nitro-compounds are prepared by the direct action of nitric acid. The reaction is greatly facilitated if a mixture of nitric and sulphuric acid is used. 

The more noble metals (for example copper, mercury and silver) can form oxides, and exhibit variable oxidation state in such compounds (for example CU2O, CuO), but it is not easy to prepare such oxides by direct action of oxygen on the metal, and elevated temperatures are necessary. Moreover, in the case of silver and mercury, loss of oxygen from the oxide by heating is easy. The oxidesare, however, basic (for example Ag20 - Ag, CuO - Cu in acids). 

Mono and Di-iubstitution Derivatives. The enolic sodium derivative of ethyl acetoacetate (E) is prepared by mixing ethanolic solutions of the ester and of sodium ethoxide. It should not be prepared by the direct action of metallic sodium on the ester, as the reaction is slow and the nascent hydrogen evolved reduces some of the ester to ethyl p4iydroxy- butyrate, CH3CH(OH)CHjCOOEt. 

Mono-substitution products of primary amines cannot easUy be prepared by direct action of the appropriate reagent for example, bromination of aniline yields largely the 2 4 6-tribomo derivative and nitration results in much oxidation. If, however, the amino group is protected as in acetanilide, smooth substitution occurs. Thus with bromine, />-bromoacetanilide is the main product the small quantity of the ortlio isomeride simultaneously formed can be easily eliminated by crystallisation. Hydrolysis of p-bromoacetanilide gives/ -bromoaniline ... 

Fluorinated Heterocyclic Compounds. HeterocycHc compounds containing the CF group are prepared by methods similar to those used in the fluorination of aHphatic compounds. The direct action of fluorine on uracil yields the cancer chemotherapy agent, 5-fluorouracil [51-21-8] as one special example of a selective fluorination on a commercial scale (25). 

Mode of Action. All of the insecticidal carbamates are cholinergic, and poisoned insects and mammals exhibit violent convulsions and other neuromuscular disturbances. The insecticides are strong carbamylating inhibitors of acetylcholinesterase and may also have a direct action on the acetylcholine receptors because of their pronounced stmctural resemblance to acetylcholine. The overall mechanism for carbamate interaction with acetylcholinesterase is analogous to the normal three-step hydrolysis of acetylcholine however, is much slower than with the acetylated enzyme. 

Lead is toxic to the kidney, cardiovascular system, developiag red blood cells, and the nervous system. The toxicity of lead to the kidney is manifested by chronic nephropathy and appears to result from long-term, relatively high dose exposure to lead. It appears that the toxicity of lead to the kidney results from effects on the cells lining the proximal tubules. Lead inhibits the metaboHc activation of vitamin D in these cells, and induces the formation of dense lead—protein complexes, causing a progressive destmction of the proximal tubules (13). Lead has been impHcated in causing hypertension as a result of a direct action on vascular smooth muscle as well as the toxic effects on the kidneys (12,13). 

Ephedrine, which is not a catecholamine, has weak oral activity as a bronchodilator and although it has some direct action at adrenergic receptors, its predominant mode of action is by displacing norepinephrine from storage vesicules. 2"Agonists which are in use or are under investigation are the result of quests for improved selectivity, retention of potency, oral activity, and longer duration of action. 

Apart from the direct action of an alcohol on a chlorosilane or siUcon, the only other commercial method used to prepare alkoxysilanes is transesterification. 

The cardiovascular adverse effects associated with quinidine therapy are hypotension and tachycardia, both of which are related to its a-adrenoceptor blocking actions. The tachycardia may be a reflex adjustment to the fall in blood pressure or may also be a direct action of the dmg on sympathetic nerve terminals leading to an increased release of NE. Quinidine also produces ringing in the ears (cinchonism) (1,2). 

Calcium channel blockers cause more pronounced lowering of blood pressure in hypertensive patients than in normotensive individuals. Generally, all calcium channel blockers cause an immediate increase in PRA during acute treatment in patients having hypertension but PRA is normalized during chronic treatment despite the sustained decrease in blood pressure. These agents also do not generally produce sodium and water retention, unlike the conventional vasodilators. This is because they produce diuretic effects by direct actions on the kidney. 

Several mucolytics reduce the viscosity of mucus by cleaving the disulfide bonds that maintain the gel stmcture. AJ-Acet l-L-cysteine [616-91 -1] (19), introduced in 1963, and mesna [19677-45-5] (20), developed in Europe in the early 1970s (20,21), are effective compounds in this class. Whereas most mucolytics must be adrninistered by aerosol, carbocysteine [638-23-6] (21), which contains a derivatized sulfhydryl group, has shown activity by the oral route (22,23). However, carbocysteine does not reduce mucus viscosity, as does acetylcysteine, but appears to have a direct action on mucus glycoprotein production (24). 

A consequence of absorption of X rays is the inner shell ionization of the absorbing atoms and the subsequent generation of characteristic X rays from the absorbing atoms, called secondary fluorescence, which raises the generated intensity over that produced by the direct action of the beam electrons. Secondary fluorescence can be induced by both characteristic and bremsstrahlung X rays. Both effects are compo-sitionally dependent. 

Staff do not work to policies but in fact work in accordance with procedures which themselves direct actions and decisions within the framework of the stated policies. In order to make the decisions required in the procedures, staff will often need to know the company policy on a particular subject, such as procurement, recruitment, release of product, licensing agreements, agreeing design changes, etc. Can they or can they not do something and if so what criteria would they satisfy ... 

Halogen-substituted olefins may be obtained from hydrazones by the action ofN-halocompounds. 327, /. 328.372 (Chloro compounds of this type may also be made by the direct action of phosphorous pentachloride on the ketone, e.g. ref. 329, 330.)... 

Ethyl Bromide.—The reid.acomcnt of llie hydropen l> halopcn fCl, Ru) may be effcelcd by the direct action of ilu halogen on the paraffin. 

Reciprocating pumps operate by the direct action of a piston on the liquid contained in a cylinder. As the liquid is compressed by the piston, the higher pressure forces it through discharge valves to the pump outlet. As the piston retracts, the ne. t batch of low pressure liquid is drawn into the cylinder and the cycle is repeated. 

By far the most common compound in the series is N3S3CI3 (yellow needles, mp 168°) which can be prepared by the direct action of CI2 (or S(3Cl2) on S4N4 in CCI4, and which is also obtained in all reactions leading to NSCl. The structure (Fig. 15.46a) is very... 

Though numerous preparative methods are possible besides the direct action of the halogen on the metal, convenient general procedures are as follows ... 

This is by far the most stable and best-known oxidation state for chromium and is characterized by thousands of compounds, most of them prepared from aqueous solutions. By contrast, unless stabilized by M-M bonding, molybdenum(III) compounds are sparse and hardly any are known for tungsten(III). Thus Mo, but not W, has an aquo ion [Mo(H20)g] +, which gives rise to complexes [MoXg] " (X = F, Cl, Br, NCS). Direct action of acetylacetone on the hexachloromolybdate(III) ion produces the sublimable (Mo(acac)3] which, however, unlike its chromium analogue, is oxidized by air to Mo products. A black cyanide,... 

Ruthenium and osmium have no oxides comparable to those of iron and, indeed, the lowest oxidation state in which they form oxides is -t-4. RUO2 is a blue to black solid, obtained by direct action of the elements at 1000°C, and has the rutile (p. 961) structure. The intense colour has been suggested as arising from the presence of small amounts of Ru in another oxidation state, possibly - -3. 0s02 is a yellowish-brown solid, usually prepared by heating the metal at 650°C in NO. It, too, has the rutile structure. 

OSF7 has been obtained as a yellow solid by direct action of the elements at 600°C... 

Flaving the d s configuration, the elements of this triad are able to conform with the 18-electron rule by forming mononuclear carbonyls of the type M(C0)5. These are volatile liquids which can be prepared by the direct action of CO on the powdered metal (Fe and Ru) or by the action of... 

Thus as in the case of oil of bergamot, esterification is accompanied by a decrease in. the total proportion of linalol and in the proportion of free acid. These facts prove that, here also, the esters originate by the direct action of the acids on the alcohols. Under these conditions, as the plant develops, part of the linalol is esterified whilst another portion is dehydrated. So that not only does the proportion of free alcohol, but also that of the total alcohol decroase. But as the esterification process is completed, which happens when the flower commences to-fade, the total alcohols increase at a fairly rapid rate. 

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