LiSE

Dinitrophenylhydra2ones usually separate in well-formed crystals. These can be filtered at the pump, washed with a diluted sample of the acid in the reagent used, then with water, and then (when the solubility allows) with a small quantity of ethanol the dried specimen is then usually pure. It should, however, be recrystallised from a suitable solvent, a process which can usually be carried out with the dinitrophenylhydrazones of the simpler aldehydes and ketones. Many other hydrazones have a very low solubility in most solvents, and a recrystallisation which involves prolonged boiling with a large volume of solvent may be accompanied by partial decomposition, and with the ultimate deposition of a sample less pure than the above washed, dried and unrecrystal-lised sample. 

Hydrolysis of benzonitrile to benzoic acid. BoU 5 -1 g. (5 ml.) of benzo-nitrUe and 80 ml. of 10 per cent, sodium hydroxide solution in a 250 ml. round-bottomed flask fitted with a reflux water condenser until the condensed liquid contains no oUy drops (about 45 minutes). Remove the condenser, and boU the solution in an open flask for a few minutes to remove free ammonia. Cool the liquid, and add concentrated hydrochloric acid, cautiously with shaking, until precipitation of benzoic acid is complete. Cool, filter the benzoic acid with suction, and wash with cold water dry upon filter paper in the air. The benzoic acid (5-8 g.) thus obtained should be pure (m.p. 121°). Recrystal-lise a small quantity from hot water and redetermine the m.p. 

Method D. Dissolve 25 g. of colourless phenylhydrazine hydrochloride (recrystal-lise, if necessary) in 250 ml. of water warming may be required. Add 45 g. of crystallised sodium acetate to the cold solution and shake until dissolved. Add 0-6 g. of decolourising carbon, shake, and filter into a dark bottle. The reagent should not be kept for longer than 1 month. 

It is essential to use freshly recrystallised benzoyl peroxide. The commercial material usually gives poor results. Commercial benzoyl peroxide may bo recrystal, lised from a small amount of hot chloroform, or by dissolving in chloroform and precipitating with absolute methyl alcohol. 

C bol the solution of re-butyl-hthium to — 35° in a Dry Ice - acetone bath and add, whilst stirring vigorously, a solution of 48 g. of ni-chlorobromo-benzene (Section IV,62) in 75 ml. of anhydrous ether. Stir for 8-10 minutes and pour the mixture with stirring on to a large excess of sohd carbon dioxide in the form of a Dry Ice - ether slush contained in a -htre beaker. Isolate the acid as detailed above for p-Toluic acid and recrystal-lise it from hot water. The yield of ni-chlorobenzoic acid, m.p. 150-151°, is 27 g. 

HBU = heat buildup, a measuie of tempeiatuie lise and lesistance to fatigue (ISO 4663/3). 

The gas is routed through heat exchangers where it is cooled by the residue gas, and condensed liquids are recovered in a cold separator at appro.ximately -90°F. These liquids are injected into the de-methanizer at a level where the temperature is approximately -90°F. The gas is (hen expanded (its pressure is decreased from inlet pressure to 22.3 psig) through an expansion valve or a turboexpander. The turboexpander Lises the energy removed from the gas due to the pressure drop to drive a compressor, which helps recompress the gas to sales pressure. The cold gas f-)50°F) then enters the de-methanizer column at a pressure and temperature condition where most of the ethanes-plus Lire in the liquid state. 

The formation of ethyl acetoacetate occurs, according- to Claisen, in four steps. The presence of a small quantity of alcohol gives lise to sodium ethylate, which forms an additive compound with ethyl acetate. The latter unites with a second molecule of ethyl acetate yielding the sodium salt of ethyl acetoacetate, and splitting off alcohol, which reacts with fresh metallic sodium. The sodium salt on acidifying passes into the tautomeric (ketonic) form of acetoacetic ester. 

The majority of aromatic sulphonic acids aie very soluble in water, and are difficult to obtain in the crystalline form On the other hand, the sodium or potassium salts generally ciystal-lise well, and it is customary to prepare them by pouiing the sulphonic acid directly after sulphonation into a strong solution of sodium or potassium chloride (Gattermann). 

The isolation and identification of 4 radioactive elements in minute amounts took place at the turn of the century, and in each case the insight provided by the periodic classification into the predicted chemical properties of these elements proved invaluable. Marie Curie identified polonium in 1898 and, later in the same year working with Pierre Curie, isolated radium. Actinium followed in 1899 (A. Debierne) and the heaviest noble gas, radon, in 1900 (F. E. Dorn). Details will be found in later chapters which also recount the discoveries made in the present century of protactinium (O. Hahn and Lise Meitner, 1917), hafnium (D. Coster and G. von Hevesey, 1923), rhenium (W. Noddack, Ida Tacke and O. Berg, 1925), technetium (C. Perrier and E. Segre, 1937), francium (Marguerite Percy, 1939) and promethium (J. A. Marinsky, L. E. Glendenin and C. D. Coryell, 1945). 

In 1938 Niels Bohr had brought the astounding news from Europe that the radiochemists Otto Hahn and Fritz Strassmann in Berlin had conclusively demonstrated that one of the products of the bom-bardmeiit of uranium by neutrons was barium, with atomic number 56, in the middle of the periodic table of elements. He also announced that in Stockholm Lise Meitner and her nephew Otto Frisch had proposed a theory to explain what they called nuclear fission, the splitting of a uranium nucleus under neutron bombardment into two pieces, each with a mass roughly equal to half the mass of the uranium nucleus. The products of Fermi s neutron bombardment of uranium back in Rome had therefore not been transuranic elements, but radioactive isotopes of known elements from the middle of the periodic table. 

In a 1959 lecture at Bryn Mawr College in Pennsylvania, Lise Meitner reflected that Life need not be easy, provided that it is not empty. Life was not easy for any Jewish woman scientist in Germany in the first half of the twentieth century, and Meitner certainly had her own experience in mind when she made this statement. 

Lise Meitner grew up in the Vienna of Emperor Franz-Josef and horsedrawn trolley cars. She was born there in 1878 into a well-to-do Jewish family and decided at an early age that she wanted to be a scientist like Madame Curie. (Later Albert Einstein would call her the German Madame Curie. ) In 1901, she entered the University of Vienna. There, where serious women students were considered odd, she was treated rudely by many of her fellow students. In 1905 she was only the second woman in the university s history to receive a Pli.D. in science. 

Crawford, D. (1969). Lise Meimer, Atomic Pioneer. New York Crown Publishers. 

Frisch, O. R. (1970). Lise Meitner. Biographical Memoirs of Fellows of the Royal Society 16 405-420. 

Sime, R. L. (1996). Lise Meitner A Life in Physics. Los Angeles University of California Press. 

Nuclear fission is a process in which a heavy nucleus—usually one with a nucleon number of two hundred or more—separates into two nuclei. Usually the division liberates neutrons and electromagnetic radiation and releases a substantial amount of energy. The discoveiyi of nuclear fission is credited to Otto I lahn and Fritz Strassman. In the process of bombarding uranium with neutrons in the late 1930s, they detected several nuclear products of significantly smaller mass than uranium, one of which was identified as Ba. The theorectical underpinnings that exist to this day for nuclear fission were proposed by Lise Meitner and Otto Frisch. Shortly after Hahn and Strassman s discovery. 

See also Electric Power, Generation of Environmental Problems and Energy Use Explosives and Propellants Meitner, Lise Military Energy Use, Historical Aspects of Molecular Energy Nuclear Energy Nuclear Energy, Historical Evolution of the Use of Nuclear Fission Fuel Nuclear Fusion Nuclear Waste. 

Enrico Fermi (Italian-American), Otto Hahn (German), F. Strassman, Lise Meitner (Austrian), and Otto Frisch (Austrian) discover and describe nuclear fission. 

The process of nuclear fission was discovered more than half a century ago in 1938 by Lise Meitner (1878-1968) and Otto Hahn (1879-1968) in Germany. With the outbreak of World War II a year later, interest focused on the enormous amount of energy released in the process. At Los Alamos, in the mountains of New Mexico, a group of scientists led by J. Robert Oppenheimer (1904-1967) worked feverishly to produce the fission, or atomic, bomb. Many of the members of this group were exiles from Nazi Germany. They were spurred on by the fear that Hitler would obtain the bomb first Their work led to the explosion of the first atomic bomb in the New Mexico desert at 5 30 a.m. on July 16,1945. Less than a month later (August 6,1945), the world learned of this new weapon when another bomb was exploded... 

In 1938, Lise Meitner, Otto Hahn, and Fritz Strassmann realized that, by bombarding heavy atoms such as uranium with neutrons, they could split the atoms into smaller fragments in fission reactions, releasing huge amounts of energy. We can estimate the energy that would be released by using Einstein s equation, as we did in Example 17.5. 

Bromopentane. Proceed as for n-Amyl Bromide, but lise 88 g. (108 ml.) of diethyl carbinol (3-pentanol), b.p. 115 5-116°. The experimental observations are similar to those given for 2-BromoperUane. C ollect the 3-bromopentane at 116-119° (120 g.). 

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