DEAD-H2

Interestingly, the corresponding azo dicarboxylate (DEAD) could be substituted to the hydrazide derivative (DEAD-H2) with equal efficiency. Unfortunately, both primary and secondary aliphatic alcohols proved to be poor substrates and only modest conversions could be achieved under these conditions, even when a larger amount of the CuCl Phen catalyst was employed (Table II, Entries 7 and 8). 

Copper-Catalysed Aerobic Oxidation of Alcohols Using DEAD H2... 

The aldehyde or ketone can now desorb, leading to the initial copper(I) hydrazide complex 13 which re-enters the catalytic cycle. The replacement of DEAD-H2 12 by DEAD 19 can be easily understood when considering this catalytic cycle. Indeed, several entries to the main catalytic cycle are possible, either via the hydrazino copper species 13 or via the direct formation of the ternary loaded complex 18 from the azo-derivative 19, Phen CuCl 3 and the alcohol 1. The key-role played by the hydrazine or azo compounds can also be readily appreciated when considering the proposed mechanistic rationale. The hydrazide, not only helps in reducing the copper(II) salt to the copper(I) state but, by virtue of its easy passage into the azo derivative, it also acts as a hydrogen acceptor, allowing the efficient oxidation of the alcohol into the carbonyl compound. 

At this stage, two major observations still need to be accounted for the lack of reactivity of aliphatic substrates and the need for a five-fold excess of DEAD or DEAD-H2 over CuCl Phen to achieve quantitative oxidations of benzylic and allylic alcohols. 

Figure 5.20 Mechanism of CuCl.phen-catalyzed oxidation of alcohols using DEAD-H2 (diethylazo dicarboxylate) as an additive.

Table adapted from ref [102]. Conditions 5 mol% CuCl, 5 mol% phenanthroline, 5 mol% DEAD-H2 (DBAD = dibutylazodicarboxylate), 2 equiv. K2CO3, gentle stream of O2, solvent is toluene, 90 °C. After 1 h reaction was complete. Isolated yields at 100% conversion. Geraniol. 

Fig. 7. NO formation for the Provo-Orem bus mn at a compression ratio of 12 1 at 30°C, 3000 rpm, where A is brake mean effective pressure B, brake thermal efficiency and C, oxides of nitrogen, (a) Effect of equivalence ratio, ( ), at a water/H2 mass ratio of 6.0 and spark = 17° before top-dead (BTC) and (b), effect of water injection where (j) = 0.60 and spark = 14°BTC. To convert MPa to psi, multiply by 14.

Scheme 12 Total synthesis of (-)-xestospongin A (116), (+)-araguspongine B (129), and (+)-xestospongin C (130) [41]. Experimental conditions i. (a) NaH, THE, (b) -BuLi, (c) 132 a. Ru(II)-S-BINAP, H2, EtOH Hi. LiBH4, Et20 iv. PPTS, 2,2-dimethoxypropane, acetone v. Nal, acetone, reflux vi. 3-picoline, EDA, THE vii. HCl(aq.), EtOH viii. TsCl, EtsN, CH2CI2 ix. Nal, butanone, reflux x. LiBH4, MeOH, i-PrOH xi. DEAD, CH2CI2 xii. H2, Ni (Raney), MeOH xiii. Rh on alumina, MeOH, H2, then add alumina, reflux...

Scheme 2-16. Synthesis of pyrrolidine. Reagents and conditions a TCDI (1,1-thiono-carbonyldiimidazole), THF b P(OEt)3, DEAD c H2, Rh/Al203, EtOH d TsOH, aq. MeOH e Bu2SnO, toluene, reflux BnBr, BmN Br f TsCl, Py, 0°C g BnNH2, A h H2, Pd(OH)2/C, EtOH.

The produced fluids and gases are typically directed into separation vessels. Under the influence of gravity, pressure, heat, retention times, and sometimes electrical fields, separation of the various phases of gas, oil, and water occurs so that they can be drawn off in separate streams. Suspended solids such as sediment and salt will also be removed. Deadly hydrogen sulfide (H2S), is sometimes also encountered, which is extracted simultaneously with the petroleum production. Crude oil containing H2S can be shipped by pipeline and used as a refinery feed but it is undesirable for tanker or long pipeline transport. The normal commercial concentration of impurities in crude oil sales is usually less than 0.5% BS W (Basic Sediment and Water) and 10 Ptb (Pounds of salt per 1,000 barrels of oil). The produced liquids and gases are then transported to a gas plant or refinery by truck, railroad tank car, ship, or pipeline. Large oil field areas normally have direct outlets to major, common-carrier pipelines. 

Scheme 4 Thomas synthesis of the smaller fragment of lb. Reagents and conditions a ent-10, SnCl4,80% b p-nitrobenzoic acid, DEAD, Ph3P, 68% c NaOH, 94% d N-phenylselenenyl phthalimide, SnCl4,60% e Bu3SnH, AIBN, 89% f H2,10% Pd/C, 70% g Dess-Martin peri-odinane h NaCl02, NaH2P04 i z-Pr2NEt, BnBr, 81% from 27 j cone. aq. HCl, MeOH, 49%...

We should also remember that not all of the states that we see when freezing the enzyme (Section 7.4) are necessarily part of the mechanism. The most stable enzyme molecule is a dead one, so we must be aware that some of the spectroscopic signals represent damaged molecules. In the [NiFe] hydrogenases, the NiA and NiB states probably are not involved in the catalytic cycle, because they react slowly, if at all, with H2. In the mechanism shown in Fig. 8.3, it is assumed that the relevant active states are NiSR, NiA and NiR. 

When YBa2Cus07 x is heated to 1000°C in a flowing atmosphere containing H2, [CAUTION The H2 should be diluted with 10 volumes of Ar to reduce the hazard of an explosion. A 10-turn 5-cm-diameter coil of glass tubing should be inserted next to the H2 tank to prevent flashback of the tank. The thermal analyzer must be purged completely so there are no dead volumes of air and the exit gas must be exhausted carefully.] reduction to BaO, Y2Os and Cu occurs (10)(25)... 

The major acid gas component is CO2, which is dead weight in a Claus plant but usually makes up 80 percent to 95 percent of the acid gas, while most of the remainder is H2S. Relatively more CO2 is produced from lower sulfur coals, or higher temperature gasifiers, or by shifting before acid gas extraction. 

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