Final condensers

The final condensation could haye gone the other way too, but it doesn t, presumably because attack on, the other carbonyl group is hindered. TM 120 is in fact piperitone, one of the flayouring principles of mint, and has been synthesised essentially by this route g.C.S... 1935, 1583 Rec. Tray. Ctum.. 1964, 464 Zhur. Obshchei Khim.. 1964, 34=... 

Final condenser Condenses the vapors to a final storage temperature of approximately 37.8 C (100 F). It uses water cooling, which means that the transferred heat is lost to the process. 

Synthesis of Quinine. This required a parallel series of operations jn which the still unknown substance Aomomeroquinenine (3-vinylpiperi-dine-4-propionic acid) replaced its dihydro-derivative, Aomocincholoipon, for the final condensation with ethyl quininate. The first step was taken by ProStenik and Prelog,who converted cinchonine to cinchqnjcjn ... 

Again, if we consider the initial substances in the state of liquids or solids, these will have a definite vapour pressure, and the free energy changes, i.e., the maximum work of an isothermal reaction between the condensed forms, may be calculated by supposing the requisite amounts drawn off in the form of saturated vapours, these expanded or compressed to the concentrations in the equilibrium box, passed into the latter, and the products then abstracted from the box, expanded to the concentrations of the saturated vapours, and finally condensed on the solids or liquids. Since the changes of volume of the condensed phases are negligibly small, the maximum work is again ... 

Another multistep protocol that initially involves the formation of fused pyrimidines (quinazolines) has been described by Besson and coworkers in the context of synthesizing 8f-/-quinazolino[4,3-b]quinazolin-8-ones via double Niementowski condensation reactions (Scheme 6.250) [437]. In the first step of the sequence, an anthranilic acid was condensed with formamide (5.0 equivalents) under open-vessel microwave conditions (Niementowski condensation). Subsequent chlorination with excess POCl3, again under open-vessel conditions, produced the anticipated 4-chloro-quinazoline derivatives, which were subsequently condensed with anthranilic acids in acetic acid to produce the tetracyclic 8H-quinazolino[4,3-b]quinazolin-8-one target structures. The final condensation reactions were completed within 20 min under open-vessel reflux conditions (ca. 105 °C), but not surprisingly could also be performed within 10 min by sealed-vessel heating at 130 °C. 

The formation of [Fe4(CO)13]2- in these systems involves a complicated series of reactions but the final condensation step is possibly related to the following reaction127 ... 

The nearest approach to the desired end is attained by repeating the process of distillation. In the case of low-boiling substances it can be done in one operation with the help of so-called fractionating columns, which are devices introduced into the gaseous phase before final condensation occurs. In the several divisions of these columns, which can be constructed in various forms (Fig. 13), vapours are liquefied by air cooling, and the vapours which are formed later must pass through this liquid which lies in their path. In this way... 

The final condensation of the glycosyl donor 5 with the acceptor 7 in dichloromethane, again using methyl triflate as... 

Reaction of the TMS-nitro compound 1496 and the indole carboxaldehyde 1497 with a catalytic amount of TBAF led to the desired alcohol 1498, which, on further treatment with TFAA, followed by elimination of the corresponding trifluoroacetate with DBU, afforded the frans-stilbene 1499. Reductive cyclization of 1499 under Cadogan-Sundberg conditions afforded the bisindole 1500. Finally, condensation of 1500 with (dimethylamino)acetaldehyde diethyl acetal led to tjipanazole D (359) in 71% yield (796) (Scheme 5.255). 

Figure 1.9 HTCVD process. Microparticles are formed in the inlet region of the system and transported to the sublimation zone, where the particles sublime to finally condense on the growth surface.

Initially segments I, II, and III were successively condensed, as were segments IV and the linear segment V. The result was two fragments which are identical to the naturally occurring BrCN cleavage products of nisin. The final condensation of these two products then afforded nisin. 

As shown in Figure 11.8, a loop of nitrogen is realized between a low-pressure zone (flash evaporator EV01, heat exchanger EC01, and bioreactor R01), a medium-pressure zone (gas/liquid separator V04), and a high-pressure zone (final condenser V05). 

Elemental sulphur from the final condensers flows to the sulphur pit where it is available in a molten state for shipment by truck transport or transfer to a storage block. Sulphur which is removed from site travels south to the Edmonton area. A significant portion is used for fertilizer production. 

The bis-diethylacetal of di-(4-oxo-n-butyl)amine (182) was obtained from y-aminobutyraldehyde diethylacetal (180) and y-chlorobutyral-dehyde acetal (181) and, after removal of acetal protecting groups, converted into 1-formylpyrrolizidine (183) without isolation of the intermediates. The final condensation was achieved by Babor et oZ.,109 who isolated 1-formylpyrrolizidine in ca. 10-15% yield at pH 4—4.5. Hydrogenation of the compound over platinum afforded 1-hydroxymethylpyrrolizidine, which they claimed to be ( + )-isoretronecanol. Leonard and Blum123 carried out the same condensation at pH 7 and reduced the resultant aldehyde, without isolation, with sodium boro-... 

Finally, condensation of phenols with various aliphatic compounds in the presence of a catalyst or a dehydrating compound, such as KHS04, H3P04, PPA, leads to 2,3-dihydrobenzofuran derivatives. It has been the subject of many investigations303-309 in the field of chemical technology. 

For a surface condenser to work properly, noncondensable vapors must be sucked out of llie shell side. This is done with a two-stage jet system, as shown in Fig. 18.3. When I was first commissioned the jets, they were unable to pull a good vacuum. Moreover, water periodically blew out of the atmospheric vent. I found, after considerable investigation, that the condensate drain line from the final condenser was plugged. 

I directed the maintenance crew to disassemble and clean the drain lines from both the final condenser (B), and the primary jet discharge condenser (A). Unfortunately, they failed to reassemble the loop seal from condenser A. But what is the purpose of this loop seal ... 

The pressure in condenser A is greater than that in the surface condenser, and less than that in the final condenser (condenser B). This means that condenser A is operating at vacuum conditions. This prevents the condensed steam formed in condenser A from draining out to atmospheric pressure, unless the condenser is elevated by 10 to 15 ft. To avoid this problem, the condensate is drained back to the lower-pressure surface condenser. To prevent blowing the noncondensable vapors back to the surface condenser as well, a loop seal is required. The height of this loop seal must be greater than the difference in pressure (expressed in ft of water) between the surface condenser and the primary jet discharge condenser (condenser A). 

We discussed before that the drain from the final condenser shown in Fig. 18.3 had plugged. Rather than unplugging the drain, could we have simply disconnected the final condenser (condenser B), and vented the discharge from the secondary jet (jet 2) to the atmosphere Would this have helped or hurt the vacuum in the surface condenser ... 

The final condenser hurts the upstream vacuum. The final condenser increases the discharge pressure from the secondary jet and thus makes the jet system work slightly harder to expel the noncondensable gas load. 

---