Structures amalgams

The electrode potential of aluminium would lead us to expect attack by water. The inertness to water is due to the formation of an unreactive layer of oxide on the metal surface. In the presence of mercury, aluminium readily forms an amalgam (destroying the original surface) which is. therefore, rapidly attacked by water. Since mercury can be readily displaced from its soluble salts by aluminium, contact with such salts must be avoided if rapid corrosion and weakening of aluminium structures is to be prevented. 

Reductions of the N —N double bond yield diaziridines and were carried out for proof of structure, using for example sodium amalgam or catalytic hydrogenation. They are unimportant beyond that, because most diazirine syntheses start with diaziridines. 

Mercury has a marked ability to bond to other metals. In addition to the amalgams aheady mentioned (p. 1206) it acts as a versatile structural building block by forming Hg-M bonds with cluster fragments of various types e.g. reduction... 

However, the cyclic structure of "hydrocotarnine acetic acid (20e) and the two condensation products of cotarnine with acetone (20f, 21) were even unambiguously determined by chemical methods alone. These compounds were not reduced either catalytically nor by sodium amalgam, although acetylhydrocotarnine acetic acid (22b) is easily reduced by both these methods. If even a small pro-... 

Okabe, T. Mercury in the Structure of Dental Amalgam , Dental Materials, 3, 1-8 (1987)... 

Light filters for colorimeters, see Filters, optical Limiting cathode potential 509 see also Controlled potential electro-analysis Linear regression 145 Lion intoximeter 747 Liquid amalgams applications of, 412 apparatus for reductions, 413 general discussion, 412 reductions with, (T) 413 zinc amalgam, 413 Liquid ion exchangers structure, 204 uses, 204, 560... 

The properties of alloys are affected by their composition and structure. Not only is the crystalline structure important, but the size and texture of the individual grains also contribute to the properties of an alloy. Some metal alloys are one-phase homogeneous solutions. Examples are brass, bronze, and the gold coinage alloys. Other alloys are heterogeneous mixtures of different crystalline phases, such as tin-lead solder and the mercury-silver amalgams used to fill teeth. 

Electrochemical processes involving metals, such as metal ion discharge and metal atom ionization, can be studied without the complications of structural changes when electrodes of the molten metal (at elevated temperatures and in non-aqueous electrolytes) or of the metal s liquid amalgam are used instead of the solid metal. 

Serious problems may arise if gallium or its liquid alloys contact aluminium alloy structural components in aircraft, when rapid amalgamation and weakening occurs. 

The first isolable alkenetitanium complex, the bis(pentamethylcyclopentadienyl)-titanium—ethylene complex 5, was prepared by Bercaw et al. by reduction of bis(penta-methylcyclopentadienyl)titanium dichloride in toluene with sodium amalgam under an atmosphere of ethylene (ca. 700 Torr) or from ( (n-C5Mc5)2Ti 2(fJ-N2)2 by treatment with ethylene [42], X-ray crystal structure analyses of 5 and of the ethylenebis(aryloxy)trimethyl-phosphanyltitanium complex 6 [53] revealed that the coordination of ethylene causes a substantial increase in the carbon—carbon double bond length from 1.337(2) A in free ethylene to 1.438(5) A and 1.425(3) A, respectively. Considerable bending of the hydrogen atoms out of the plane of the ethylene molecule is also observed. By comparison with structural data for other ethylene complexes and three-membered heterocyclic compounds, the structures of 5 and 6 would appear to be intermediate along the continuum between a Ti(11)-ethylene (4A) and a Ti(IV)-metallacyclopropane (4B) (Scheme 11.1) as... 

The 3,6-anhydro-D-glucose (XIX) of Fischer and Zach13 on reduction with sodium amalgam or with hydrogen in the presence of Raney nickel14 gives 3,6-anhydro-D-sorbitol (XX), a method of synthesis which establishes the ring structure of the substance since that of 3,6-anhydro-D-... 

One of the dianhydrohexitols, B, was identified with l,5 3,6-dianhy-dro-D-mannitol (neomannide, see below), but the other two, A and C, remain of unknown structure. An interesting observation concerning the dianhydride A has been made.48 When l,6-dichloro-l,6-didesoxy-D-mannitol was treated with sodium methoxide a new crystalline dianhydrohexitol was obtained. This had m. p. 118-119° but showed la]D + 33.6°. It was therefore the enantiomorph of dianhydride A. Furthermore, when dichloro-didesoxy-D-mannitol is treated with sodium amalgam yet another dianhydride was isolated. This had m. p. 118-119° and fa]D + 93.6° and is doubtless identical with the /3-mannide of Siwoloboff.49... 

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