Total yield

variations in the total yield (measured with a photomultiplier) should reflect variations in p. 

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A considerable amount of the formic acid, however, still remains behind in the distilling-flask as the unhydrolysed monoformate. Therefore, if time allows, dilute the residue in the flask with about an equal volume of water, and then steam-distil, the monoformate ester being thus completely hydrolysed and the formic acid then driven over in the steam. Collect about 400 ml. of distillate. Add this distillate to that obtained by direct heating of the reaction mixture and then treat with lead carbonate as described above. Total yield of lead formate is now about 40 g. 

Add about 60 ml. of petroleum (b.p, 60-80°) with stirring to the fraction of b,p, 150-180°, thus precipitating the pure anhydrous pinacol (2 5-3 8 ) Filter this off, and then shake the filtrate with ca. 4 ml, of water the remaining pinacol now separates as the hexahydrate (5 g.). The two crops may be united and recrystallised from ca. 10 ml, of water (total yield of hexahydrate, 8-9 g,). Dry and bottle the product rapidly as described in (a). 

Di-n-amyl ether. Use 50 g. (61 5 ml.) of n-amyl alcohol (b.p. 136-137°) and 7 g. (4 ml.) of concentrated sulphuric acid. The calculated volume of water (5 ml.) is collected when the temperature inside the flask rises to 157° (after 90 minutes). Steam distil the reaction mixture, separate the upper layer of the distillate and dry it with anhydrous potassium carbonate. Distil from a 50 ml. Claisen flask and collect the fractions of boiling point (i) 145-175° (13 g.), (ii) 175-185° (8 g.) and (iii) 185-190° (largely 185-185-5°) (13 g.). Combine fractions (i) and (u), reflux for 1 hour in a small flask with 3 g. of sodium, and distil from the sodium amyloxide and excess of sodium this yields 9 5 g. of fairly pure n-amyl ether (iv). The total yield is therefore 22 - 5 g. A perfectly pure product, b.p. 184 185°, is obtained by further distillation from a Little sodium. 

Equip a 1 Utre three-necked flask or a 1 litre bolt- head flask with a reflux condenser and a mercury-sealed stirrer. Dissolve 50-5 g. of commercial 2 4-dinitro-l-chlorobenzene in 250 ml. of rectified spirit in the flask, add the hydrazine solution, and reflux the mixture with stirring for an hour. Most of the condensation product separates during the first 10 minutes. Cool, filter with suction, and wash with 50 ml. of warm (60°) rectified spirit to remove unchanged dinitrochlorobenzene, and then with 50 ml. of hot water. The resulting 2 4-dinitrophenylhydrazine (30 g.) melts at 191-192° (decomp.), and is pure enough for most purposes. Distil oflF half the alcohol from the filtrate and thus obtain a less pure second crop (about 12 g.) recrystallise this from n-butyl alcohol (30 ml. per gram). If pure 2 4-dinitrophenylhydrazine is required, recrystallise the total yield from n-butyl alcohol or from dioxan (10 ml. per gram) this melts at 200° (decomp.). 

The total yield of crude acetylmethylurea may be used without drying. 

That some modification to the position so far described might be necessary was indicated by some experiments of Nesmeyanov and his co-workers. Amongst other compounds they nitrated phenyl trimethyl ammonium and triphenyloxonium tetrafluoroborates with mixed acid the former gave 96 % of m- and 4 % of -nitro compound (88 % total yield), whilst the latter gave 80% of the tri-(p-nitrophenyl)oxonium salt. Ridd and his co-workers have made a quantitative study of the phenyl trimethyl ammonium ion. Their results, and those of other recent workers on the nitration of several cations, are collected in table 9.3. 

At 25 °C unless otherwise stated. t The total yield of nitroquinolines was about 94%. An unidentified yellow com- ... 

The case of i-methyl-4-quinolone is puzzling. The large proportion of the 3-nitro isomer formed in the nitration (table 10.3 cf. 4-hydroxyquinoline) might be a result of nitration via the free base but this is not substantiated by the acidity dependence of the rate of nitration or by the Arrhenius parameters. From r-methyl-4-quinolone the total yield of nitro-compounds was not high (table ro.3). 

Yield isosafrole, 60 grams (12%) TOTAL-MDP2P, 338 grams (37.6%) The smaller portion i/i/as distilled in a 500 mL flask and yielded another 30 grams. Total yield 79.6% / 67.6% (MDP2P) + 12% (ISOSAFROLE). 

Then N-Boc-O-benzylserine is coupled to the free amino group with DCC. This concludes one cycle (N° -deprotection, neutralization, coupling) in solid-phase synthesis. All three steps can be driven to very high total yields (< 99.5%) since excesses of Boc-amino acids and DCC (about fourfold) in CHjClj can be used and since side-reactions which lead to soluble products do not lower the yield of condensation product. One side-reaction in DCC-promoted condensations leads to N-acylated ureas. These products will remain in solution and not reaa with the polymer-bound amine. At the end of the reaction time, the polymer is filtered off and washed. The times consumed for 99% completion of condensation vary from 5 min for small amino acids to several hours for a bulky amino acid, e.g. Boc-Ile, with other bulky amino acids on a resin. A new cycle can begin without any workup problems (R.B. Merrifield, 1969 B.W. Erickson, 1976 M. Bodanszky, 1976). 

The major problem in such conversions is the degradation of the branched carbon side-chain on C-17 which is present in all abundant steroids and lacking in all steroid hormones. The most important starting material used in industry today is diosgenin from the Mexican dioscorea plant. It is degraded by the method of Marker to 16-dehydropregnenolone in 45% total yield. This compound is a key substance in the production of several hormones with anabolic, catabolic, and sexual effects. 

Monosubstitution of acetylene itself is not easy. Therefore, trimethylsilyl-acetylene (297)[ 202-206] is used as a protected acetylene. The coupling reaction of trimethylsilylacetylene (297) proceeds most efficiently in piperidine as a solvent[207]. After the coupling, the silyl group is removed by treatment with fluoride anion. Hexabromobenzene undergoes complete hexasubstitution with trimethylsilylacetylene to form hexaethynylbenzene (298) after desilylation in total yield of 28% for the six reactions[208,209]. The product was converted into tris(benzocyclobutadieno)benzene (299). Similarly, hexabutadiynylben-zene was prepared[210j. 

For any one ion type (e.g., Cs ), measurement of its abundance in a sample requires the sample to be evaporated over a period of time. The total yield of ions is obtained by integrating the area under the ion-yield curve (Figure 7.8c). 

Geochemical studies of sulfate ia streams have beea approached ia various ways. For example. Ref. 17 is a review of Hterature oa sources of sulfate ia the dissolved loads of streams, especially ia areas where developmeat effects are likely to be stroag. It was coacluded that for North America as much as 60% of the average yield of sulfate carried to the ocean is related to human activities. This study assigned a higher proportion of the total yield of sulfate ia European streams to human sources, but for other continents it was thought the effects of human activities to be relatively minor. 

Peat Waxes. Peat waxes are much like montan waxes in that they contain three main components a wax fraction, a resin fraction, and an asphalt fraction. The amount of asphalt in the total yield is influenced strongly by the solvent used in the extraction. Montan waxes contain ca 50 wt % more of the wax fraction than peat waxes, and correspondingly lower percentages of the resin and asphalt fractions. The wax fraction in peat wax is chemically similar to that of the wax fraction in montan wax. 

The stirrer is started and there is added rapidly a cold sulfuric acid solution made by adding enough ice to 200 cc. of concentrated sulfuric acid (sp. g. 1.84) (Note 7) so that some of the ice is not melted. The stirring is continued for five or ten minutes or until the yellow lumps of the sodium salt disappear. The mixture is then extracted with three 600-cc. portions of benzene (Note 8). The benzene is destilled (Note g) from the extracts on a water bath and the residue is transferred to a special 2-I. Claisen flask (Org. Syn. 1, 40) and distilled under diminished pressure. The product boils at i3o-i32°/37 mm. or ii7-iig°/2g mm. A small high-boiling fraction is redistilled to yield 20-30 g. more of the ethyl acetopyruvate. The total yield is 480-520 g. (61-66 per cent of the theoretical amount). 

The combined product is mixed with i 1. of 20 per cent sodium hydroxide solution and stirred on the steam bath for four hours, in order to hydrolyze a small proportion of heptyl acetate. The oil is then separated and distilled, and the portion boiling at 172-176° collected. The residue in the flask is mixed with about 100 cc. of water and distilled, whereupon a further small quantity of oil passes over with the steam. This distillate and the forerun are freed of the bulk of the water in a separatory funnel, and distilled from a smaller flask. In this way the total yield of -heptyl alcohol boiling at 172-176° (uncorr.) is 350-370 g. (75-81 per cent of the theoretical amount). The alcohol may be redistilled under reduced pressure, and it passes over almost without loss at 7i-72°/i2 mm. 

The total yield amounts to 260-266 g. (48.5-49.5 per cent of the theoretical amount). The product is contaminated by slight traces of d-glucose and possesses a very faint reducing power towards Fehling s solution. For complete purification it is recrystallized (with practically no loss and practically no change in melting point) from five parts of methyl alcohol with the use, if necessary, of decolorizing carbon. 

In a 500-cc. round-bottom flask fitted with a reflux condenser are placed 68 g. of phenylurea (0.5 mole) (Note i) and 120 cc. (i mole) of 42 per cent hydrazine hydrate solution (Note 2). The flask is heated on a steam bath for about twelve hours. The hot mixture is treated with a small amount of decolorizing charcoal (Norite) and filtered. The charcoal is washed with two 15-CC. portions of warm water and the filtrate and washings are then concentrated on a steam bath to about 100 cc. On coolipg in an ice bath a crop of crystals separates and is collected on a filter and washed with two 15-cc. portions of cold water. The filtrate and washings are concentrated to about 25 cc. and another crop of crystals is obtained as before. The total yield of crude compound is 47-52 g. It is white at first but sometimes turns brown on drying. It usually melts below 115° because of some unchanged phenylurea. 

This material Is purified by recrystallization from ethyl acetate acetone 2 1 (v v) to give a first crop (6.8 g), and by flash chromatography of the residue from the mother liquor, using 150 g of 230-400 mesh silica gel (Merck), a 40-mm diameter column, and elution with 10 1 (v v) ethyl acetate methanol. A fast moving orange band and a slower moving lemon-yellow band can be clearly seen on the column. The lemon-yellow hand is collected from the column and evaporation gives a second crop (1.4 g) of comparably pure material. The total yield of the pale yellow isoquinoline is 8.2 g (86t), mp 135-137°C (Note 10). 

In a 3-I. round-bottomed flask are placed 500 cc. (400 g., 8.7 moles) of absolute alcohol which has been saturated in the cold with hydrochloric acid gas (Note i), 870 cc. (6S0 g., 20 moles) of 96 per cent alcohol (Note 2) and 70 g. (1.03 moles) of methyleneaminoacetonitrile (Note 3). This mixture is refluxed on a steam bath for three hours (Note 4). During the refluxing, ammonium chloride separates. After the reaction is complete, the hot alcohol solution is filtered with suction and the filtrate cooled, thus allowing the glycine ester hydrochloride to separate out in fine white needles. The product is filtered with suction, sucked as dry as possible on the filter, and then allowed to dry in the air. The yield is about no g. The alcohol from the filtrate is distilled (Note 5) until about one-third of its volume is left and again cooled and a second crop of crystals is obtained. The total yield of product, m.p. 142-143, varies from 125 to 129 g. (89-91 per cent of the theoretical amount). If a very pure product is desired, it may be recrystallized from absolute alcohol. 

Catalyst obtained from Engelhard Industries was used. The submitters used 200 mg. of Fluka 10% palladium on charcoal catalyst with 5 g. of starting material in 250 ml. of ethanol and obtained a total yield of 2.3 g. (46%), m.p. 208-211°. 

This procedure is then repeated again. Distillation of the combined residues using a nitrogen leak (Note 16) yields 54 g. of the product as a yellowoil, b.p. 66-68° (1.1 mm.) (Note 17). The distillation residue, when washed through a short acidic alumina column with light petroleum ether and the solvent evaporated, yields an additional 5 g. of product total yield 59-68 g., 67-78% (Notes 18, 19). 

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