Needle compounds

The amino add analysis of all peptide chains on the resins indicated a ratio of Pro Val 6.6 6.0 (calcd. 6 6). The peptides were then cleaved from the resin with 30% HBr in acetic acid and chromatogra phed on sephadex LH-20 in 0.001 M HCl. 335 mg dodecapeptide was isolated. Hydrolysis followed by quantitative amino acid analysis gave a ratio of Pro Val - 6.0 5.6 (calcd. 6 6). Cycll2ation in DMF with Woodward s reagent K (see scheme below) yielded after purification 138 mg of needles of the desired cyc-lododecapeptide with one equiv of acetic add. The compound yielded a yellow adduct with potassium picrate, and here an analytically more acceptable ratio Pro Val of 1.03 1.00 (calcd. 1 1) was found. The mass spectrum contained a molecular ion peak. No other spectral measurements (lack of ORD, NMR) have been reported. For a thirty-six step synthesis in which each step may cause side-reaaions the characterization of the final product should, of course, be more elaborate. 

However, prior protective acetylation of the amino group leads to a good yield of the 5-nitro compound [2-acetamido-4-methyl-5-nitroselenazole, m.p. 185 C (19)j. Similarly. 2-diethylamino-4-methy)-selenazole with nitric acid gives the. 5-nitro derivative [vellow needles, m.p. 93°C (26)],... 

Dichloronitrobenzene. This compound crystallizes in needles from ethanol and has both a stable and labile form. The stable a-form has... 

Strong acids and strong alkaUes can severely bum the skin, chromium compounds can produce skin rashes, and repeated exposure to solvents causes removal of natural oils from the skin. Infection is always a concern for damaged skin. Absorption through the skin is possible for materials that are appreciably soluble iu both water and oil, eg, nitrobenzene, aniline, and tetraethyllead. Other materials can be absorbed if first dissolved iu extremely good solvents, eg, dimethyl sulfoxide. Subcutaneous iujection can occur accidentally by direct exposure of the circulatory system to a chemical by means of a cut or scratch or iuadvertent penetration of the skin with a hypodermic needle. 

Benzenetetrol. 1,2,3,5-Tetrahydroxybenzene (64) forms needles (mp 165°C) from water. The compound is easily soluble ia water, alcohol, and ethyl acetate and is iasoluble ia chloroform and benzene. In aqueous potassium bicarbonate solution sparged with carbon dioxide,... 

Amino-4,6-dichlorophenol. This compound (11) forms long white needles from carbon disulfide, and aggregate spheres from benzene. It sublimes at 70—80°C (8 Pa = 0.06 mm Hg) and decomposes above 109 °C. It is freely soluble in benzene and carbon disulfide, and is sparingly soluble in petroleum ether, water, and ethanol. The free base is unstable and the hydrochloride salt (mp 280—285°C, dec) is employed commercially. 

Parts made from fluoroelastomers ate used ia appHcations that justify their high cost, usually where the maintenance and replacement costs are high enough to offset the initial cost of the part. These include automotive appHcations such as valve stem seals, fuel injector components, radiator, crankcase and transmission seals, and carburetor needle tips. Numerous seals and gaskets in the marine, oilfield, and chemical processing industries employ fluoroelastomers. In addition, many hoses in the automotive and chemical industry are made entirely of fluoroelastomer compounds or have a veneer of the fluoroelastomer as a barrier exposed to the harsh environment. Seals and gaskets in military appHcations and the binder for flares and missile appHcations ate made with fluoroelastomers. 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

If the material is not partly dried before hydrolysis, the yield of the hydrochloride is diminished because of its solubility. If pure 3-bromo-4-acetaminotoluene is desired, the crude material may be crystallized from 50 per cent alcohol with the addition of decolorizing carbon (Norite) as almost colorless needles, m.p. 116-117°, The yield is 360 g, (79 per cent of the theoretical amount). This purification has no advantage when the acetam-ino compound is to be hydrolyzed to the amine. 

About two-thirds of the carbon tetrachloride is distilled. The solution is cooled, and the crystals of />-nitrophenyl isocyanate are filtered as quickly as possible in order to avoid prolonged exposure of the compound to the moisture of the air. By concentration of the mother liquor a further crop is obtained. The product is recrystallized from dry carbon tetrachloride and is obtained in the form of light yellow needles melting at 56-57° (Note 6). The yield after one recrystallization is 152-170 g. (85-95 P r cent of the theoretical amount) (Note 7). 

In order to obtain the sodium compound, 6 grams of the product are ground in a moitar with i gram of sodium carbonate, placed in a beaker, and moistened with alcohol. Five c.c. of water are added and the nii.xture boiled until the evolution of carbon dioxide ceases. To the sodium salt 25 c.c. spirit are added and the mixture boiled and filtered. On standing for a day or two, the sodium salt crystallises in brown needles. 

Reaction.—kAd a drop of feriic chloride to the aqueous solution of the aldehyde. A deep violet colouration is producecl p-Hydi-oxybcnsaldehyde.—Colouiless needles, m. p. 115—1 16 scarcely soluble in cold water, readily in hot water, alcohol ether. Non-volatile in steam. The bisulphite of sodiutaa compound dissolves readdy in water. 

The fi-compound is dissolved in 50 c c. pure dry ether, and dry hydiogen chloride is passed in with constant shaking to prevent the delivery tube from becoming blocked. Colourless crystals of the hydrochloride of the /3-o ime separate and aie filtered and washed with dry ether and then placed in a separating funnel and covered with a layer of ether. A. concentrated solution of sodium carbonate is gradually added with constant shaking until no further effervescence is observed. Sodium chloride is precipitated and the /3-oxime dissolves in the ether. The ether extract is sepaiated, dehydrated over sodium sulphate, and the ether remoi ed as rapidly as possible at the ordinary temperature by evaporation in vacuo. The residue crystallises, and when pressed on a porous plate leaves a mass of small silky needles, m. p. 126—130A It may be re-... 

By far the most common compound in the series is N3S3CI3 (yellow needles, mp 168°) which can be prepared by the direct action of CI2 (or S(3Cl2) on S4N4 in CCI4, and which is also obtained in all reactions leading to NSCl. The structure (Fig. 15.46a) is very... 

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