16. (the two ; the three . .) , : the two molecules , .
:
, . Carboxylic acids exist normally in dimeric form with very strong hydrogen bridges between the carbonyl and hydroxyl groups of the two molecules.
. This plane of symmetry is midway between the two asymmetric carbons.
. Semiprojection formulas for the three tartaric acids are shown on the following page.
, . The close agreement of the six compounds is unlikely to be a coincidence.
, . The two carboxyl groups have been shown to be on the same side of the molecule.
. The three chromatographic techniques have thus far been presented in the simplest possible terms.
, , . The proportion in which the four possible products are formed presents a very complicated problem.
, ,
90- . The four hexilols were known to be isomeric, but their relationship to each other and to the five natural C6 sugars was not known until Fischer's classical work in the early nineties.
17. , . , , (. 15), , , . . , , , : work, power, evidence, measurement, temperature, percentage, potential, speed, data, power, polymerisation, substitution, concentration, synthesis, acetolysis.
:
. The speed of the polymerisation runs parallel with the susceptibility to hydrolysis.
1944 . The work was completed early in 1944.
, . So long as peroxide was present in the reaction mixture the substitution proceeded rapidly.
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, . It is to be noted that the data approach the limiting law at low values of the concentration.
. Prior to the extraction the urine must be strongly acidified with hydrochloric or sulfuric acid.
1948 . The synthesis was not completed until 1948.
, , . The percentage of the ions, which are reflected from the first dypode decreases as the energy is increased.
. The point of equilibrium however is tremendously influenced by the temperature.
, , . By increasing the length, the separating power of the column improves, but not to a proportional degree, because other operating variables are also affected.
18. , , . , , . :
. The radicals are still observable in the polymer after as long as three months.
. The halogen must be ionized to some extent.
. The bromide may be treated with potassium iodide to give the corresponding iodide.
, II . The ketone II was found to be identical in every respect with androsteron.
. The hydroxythiophenes are inherently unstable.
, . The nickel was probably unessential in this reaction.
4 - , 4 - 33%- . When the 4-lithium derivative is treated with ethylmagnesium halide anol oxygen, a 33% yield of the 4-hydroxy-dibenzothiophene is obtained.
. The diacetate crystals slowly dissolve as the phenolic hydroxyl group is liberated.
. As the ammonia evaporates, both layers gradually disappear.
7- , . The 7- keto acid adds bromine, if slowly.
α- . The bromine may replace either of the two α-hydrogens in the dextro acid.
, RM . In like manner, it is possible to compare the salts or RM compounds.
. The spirans may be made in good yield.
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, 3- 4- - . Structural models indicate that the nitrogen and hydroxyl groups are too far apart in the 3- and 4-hydroxypyridine.
. The effect of the acetolysis on glucose was tested.
. Removal of the hydroxyl group requires little activation.
, - . Conspicuously enough, hydroquinone had never yet been isolated from the p-disubstituted compounds.
150 . Ethyl iodide and silver sulfate at 150 give a fair yield of the ester.
, . Towards both palladium and platinum the diene behaves as chelating group.
, . These reactions are common to the sulfates.
, , . If the thioester is saponified with sodium hydrosulfide, sodium thioacetate is regenerated and may be used for making more of the ester.
19. : the double bond, the replacement of hydrogen. , (. 9), , . 1:
XXIX, , , . The bridged species XXIX might represent either an unstable intermediate or the transition state of the reaction.
:
. In this medium the antimony wave is well in advance of the lead wave.
. The equilibrium constant and the forward rate constant.
, , . When the crystal system but not the cell dimensions is known.
1 . . . , . . . . ., . 61.
. The second difficulty is concerned with the electrometric determination.
, . The yield is notably better with the secondary than with the primary iodide.
, , . In the Grignard process formaldehyde and ethylene oxide give primary alcohols, aldehydes afford secondary alcohols, and both ketones and esters yield tertiary alcohols.
α- , . The reaction is reversible and hence leads to a configurational change of the α-asymmetric carbon atom whereas the other asymmetric carbon atoms are unaffected.
- . In the reaction between ethyl orthoformate and acetone the product was the conventional ketal.
-2- . The supposed cis-2-methyl-cyclohexanol was in reality methylcyclopentylcarbinol.
. Attempted resolutions with the active hydroxyhydrinamines also failed.
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. The quaternary compounds of just this type are almost unknown.
, , . The neutral carbon diradical might well be added to the list.
. The nitro compound is still optically active.
, , , , , , . The tropylium ion was long ago predicted to be a stable cation and is probably at least as stable as the benzyl ion.
2-, , . The optically active 2-benzylbutane is probably of the inverted configuration.
. In the aromatic series, the use of methanol and sulfuric acid is exemplified in the commercial process for making dimethylaniline.
, , . A variety of other reactions also take place, notably the direct formation of the alkyl disulphide together with nitric oxide or hydroxylamine hydrochloride.
20. , , of (., , 30).
:
. The isolation of the nucleoprotein from the cell.
. The divinyl ether of ethylene glycol is not readily obtained in good yields.
. This is shown by the data of Gross on the salt effect on the activity coefficients of acetone.
, , . The reaction runs smoothly as soon as some of the nitric acid is replaced by the water of nitration.
, , , . Certain structural factors such as the size of the groups in the diphenyls must be taken into consideration.
. The substitution of oxalic for sulphuric acid supplies an interesting example of oxycellulose formation.
, , . It is believed that the reaction proceeds by the transfer of the phenyl group as a neutral entity, rather than as an ion.
, . The polarization of these lines can be predicted from wave mechanical considerations.
, , . The oxidation of alkylthiophenes. while giving very low yields, has been widely used in the past.
. The activity / the hydroxyl group increases markedly with rise in temperature.
A. The synthesis of A was a first objective of the research.
4 . . 49
, , . The sulfonation of a number of other sulfones is mentioned incidental to reactions in which sulfonic acids are the principal products.
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- . In the description of catalysis as a physico-chemical phenomenon, three factors should be considered.
. The chlorination of toluene in the aromatic nucleus requires quite different catalysts.
. Addition reactions to carbonyl compounds almost invariably involve the attack of a nucleophilic reagent on the carbonyl carbon atom.
, α-1,6- , . The isolation of isomaltose and its higher homologues proved that the α-l,6-linkage is present and can occur in dextrans but there is only one case on record of the isolation and examination of a disaccharide other than isomaltose.
, , . Brooks has studied the oxidation of phenanthrene over catalysts consisting of V2O5 on silica gel with and without K2SO4.
, . The occurrence of a band here is not evidence for the presence of an anhydride, as many other types of compound can give rise to strong bands in this region.
. They observed the production of a mere trace of active free chlorine atoms.
, . The addition of hydrogen bromide may take either a homolytic or a heterolytic course.
. One of the objectives of the present investigation was the preparation of substituted polyfluoronaphtbalenes.
RM- -. Part of the case for the intermediate
formation of RM-compounds rests on the capture of such compounds during the Wurtz-Fittig reaction.
. Measurements of diffusion coefficients are needed for the proper interpretation of sedimentation constants.
. This is the type of work carried out by Pines on the isomerization of hydrocarbons.
. Given suitable conditions, this enzyme can catalyse the dehydrogenatiou of many different aldehydes.
. Such phenomena have nothing whatsoever to do with the acidity of the solutions.
. The reaction is really the conversion of nonsolvated molecules into solvated ions.
, Butyrolactone was of considerable importance as a chemical intermediate for the synthesis of substitutes for citric acid.
. The phthalimide reactions are no longer used for the synthesis of glycine.
, . The formation of the acetone, along with carbon dioxide, fixes the structure as having a branched chain.
. In contrast, ultraviolet-inactivated phages do not interfere with the multiplication of active phage.
, . It might be that the alkylation of thiophene with olefins involves a copolymerization mechanism.
. Substituents may increase the stability of one form over the other.
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- . The bromide ion occupies the proper position for the formation of a new tetrahedron.
,
4* 51
. This reaction is about the only practical method for studying the acidity of such very weak acids as the hydrocarbons.
, 14β- 14β-. Our objective to effect the conversion of the resulting 14α-hydroxy steroids to the corresponding 14β-hydroxy compounds.
21. , , of (. 20), , , ( , III , . 191) .
:
. The nitration in acetic acid solution was definitely first-order.
. The groups on the nitrogen atom make very little difference.
, . The copolymerisation with indoles may also have a bearing on the structure of natural and enzymically produced melanins.
, , . The carbon carrying the chlorine in the product is inverted as compared to the starting material.
. The double bonds of the diolefins produced are always adjacent to one another.
, , . The dihydrocompound resulting from the reduction of the carbonyl group of the hormone is three times as active as androsteron.
, . The unsaturated hydrocarbon produced is found to be essentially pure methylacetylene.
, , . The technique adopted by these workers for the examination of fats consisted in the following.
. Diethylphenylphosphine, of the phosphines tried, gave the most readily crystallisable derivatives.
, , () . Here, as above, the intermediates are drawn to express the evidence available and are therefore only tentative forms.
22. all both.
:
, . This scheme has the disadvantage that it does not take into consideration all the possibilities.
, . Paper chromatography showed that all the thiophosphate had been hydrolysed.
14β. Nearly all the naturally occurring cardiac-active steroidal lac-tones possess a 14β-hydroxy substituent.
, . For some time past esters of carbohydrates have been known which do not exhibit all the properties of a normal ester.
, , , . We have studied both the reactions that are considered to lead to the compound under investigation.
23. , :
1) , , , , , . : The Pacific (Ocean), The Atlantic (Ocean), The Caspian (Sea), The Mediterranean (Sea), The Thames (The Thames River), The Volga.
1. lake (.), loch (.) lough (.), . : The Baikal, Lake Baikal; the Leman, Lake Leman; Lake Balaton, Lake Ohio, Lake Ontario, Loch Katrine.
2. , : + on (upon) + + , : Stratford-on-Avon, Newcastle-upon-Tyne.
2) ( , ): The West Indies, The Philippines, The Canaries, The Hebrides;
3) ( , ): The Urals, The Alps;
4) : The Sahara, The Gobi;
5) , , , : The Netherlands, The Congo, The Argentine, The Sudan, The Transvaal, The Lebanon, The Ruhr, The Crimea, The Caucasus, The Hague, The Strand, The Mall .
6) , , (sea, ocean, gulf, cape, etc.): The Black Sea, The Persian Gulf, The Suez Canal, The Gulf of Mexico, The Cape of Good Hope, The Soviet Union, The United States, The United Kingdom (: Hudson Bay, Hudson Strait, Cape Horn);
7) , , : The Sedov, The Georgia, The Metropol, The Astoria, The Times, The Manchester Guardian, The Daily Herald, The Northern Review, The Pravda, The Moscow News (: Daily Worker).
24. , , , .
: , , , , , , , , .
25. , , , , (. , 1821). :
I , . In structure I one hydrogen is attached to oxygen and therefore is different from the other five, which are linked to carbon.
. Steam entrains aniline and carries it over into the receiving flask.
, . Water
and hydrochloric acid were then added to dissolve out the zinc chloride, and the system taken up with hot alcohol until the residue, after cooling, was solid.
, , , , . If anything this water content is probably underestimated, because sucrose may extract water from phage.
, . It appears first that non-ionic polar groups in sulphonate anions can form hydrogen bonds to casein in water over quite a wide pH range.
. Ethyl acetate was formed, and with it ethyl trichlorosilane.
. Hydroxymethylenecamphor reacts analogously.
. , , . . . , , . : sucrose sucroses, carbon carbons, aniline anilines, acid acids, acetate acetates, silane silanes, benzaldehyde benzaldehydes . .
