Acidic melts

Dissolve 10 g. of lactose (1) in 100 ml. of nitric acid, sp. gr. 115, in an evaporating dish and evaporate in a fume cupboard until the volume has been reduced to about 20 ml. The mixture becomes thick and pasty owing to the separation of mucic acid. When cold, dilute with 30 ml. of water, filter at the pump and set the filtrate A) aside. Wash the crude acid with cold water. Purify the mucic acid by dissolving it in the minimum volume of dilute sodium hydroxide solution and reprecipitating with dilute hydrochloric acid do not allow the temperature to rise above 25°. Dry the purified acid (about 5 g.) and determine the m.p. Mucic acid melts with decomposition at 212-213°. 

The suspension of phenylacetamide may be further hydrolysed to phenylacetic acid by refluxing with stirring until the solid dissolves. The mixture becomes turbid after 30 minutes and the product begins to separate as an oil refluxing is continued for 6 hours, the mixture is cooled first with tap water and then by an ice-water bath for about 4 hours. The crude phenylacetic acid is filtered at the pump, washed with two 50 ml. portions of cold water, and dried in a desiccator. The resulting crude acid melts at 69- 70° it may be purified by recrystallisation from light p>etroleum (b.p. 40-60°) or, better, by vacuum distillation. 

Benzilic acid melts at 149-150°, i.e., very close to that of diphenylacetic acid. The completeness of the reduction can easily be tested by treating a little of the product with concentrated sulphuric acid if even a trace of benzilic acid remains, the sulphuric acid will have a rod colour. 

Amino acid Melting point, °C Density, [ ]d t, °C f,% Solvent... 

Traditionally, sodium dichromate dihydrate is mixed with 66° Bh (specific gravity = 1.84) sulfuric acid in a heavy-walled cast-iron or steel reactor. The mixture is heated externally, and the reactor is provided with a sweep agitator. Water is driven off and the hydrous bisulfate melts at about 160°C. As the temperature is slowly increased, the molten bisulfate provides an excellent heat-transfer medium for melting the chromic acid at 197°C without appreciable decomposition. As soon as the chromic acid melts, the agitator is stopped and the mixture separates into a heavy layer of molten chromic acid and a light layer of molten bisulfate. The chromic acid is tapped and flaked on water cooled roUs to produce the customary commercial form. The bisulfate contains dissolved CrO and soluble and insoluble chromic sulfates. Environmental considerations dictate purification and return of the bisulfate to the treating operation. 

The yield of pure white mandelic acid melting at 118° is 229-235 g. (50-52 per cent of the theoretical amount based on benzaldehyde). 

The yield is 147-160 g. (68-74 per cent of the theoretical amount). It sinters at 190-191° and melts at 199-200° (corr.). A sample twice recrystallized from glacial acetic acid melted at 200-202° (corr.) (Note 3). The crystal form of this product compares very favorably with that of quinizarin of the highest purity, as observed under the microscope. 

The checkers found that 4-hydroxy-3,5-diiodobenzoic acid may be made from 4-hydroxybcnzoic acid using the above directions with the exception that the product is not recrystallized from acetone, in which it is only slightly soluble. The yield of 4-hydroxy-3,5-diiodobenzoic acid melting at 278-279° with decomposition is 59 g. (84 per cent of the theoretical amount). 

The resulting -aminocaproic acid is collected on a suction filter and dried in a desiccator. The yield of -aminocaproic acid melting at 201-203° is 52.5-53.5 g. (90-92 per cent of the theoretical amount). 

The crude ester, after a further washing and after being dried in a vacuum desiccator over sulfuric acid, melts at 98-100 and weighs 220 g. (91 per cent of the theoretical amount). 

The amino acid and the ammonium chloride may conveniently be separated by passing through a column of ion-exchange resins. The amino acid melts at 195°C. 

Maleic anhydride is commonly prepared by passing a mixture of benzene vapour and air over a catalyst (e.g. a vanadium derivative) at elevated temperatures (e.g. 450°C). It is a crystalline solid melting at 52.6°C (the acid melts at 130 C). 

J ropi ) fics.- Vhc, acid, nhich contains i molecule of water, crystallises in prisms soluble in water, alcohol, and also mo-cleralely soluble in ether m. p. looA The anhydrous acid melts at 153—154. ... 

T. A. O Donnell, Superacids and Acidic Melts as Inorganic Chemical Reaction Media, VCH, New York, 1992, 243 pp,... 

Archer, owing to very unfortunate coincidences, had mistaken acid potassium tartrate for the acetylamino acid. Goldfarb et al. prepared authentic 5-acetylamino-2-thiophenecarboxylic acid, mp 230 232°C (methyl ester, mp 171-171.5°C ethyl ester, mp 161°C), through reduction of 5-nitro-2-thiophenecarboxylic acid with Raney nickel in acetic anhydride and proved the structure by Raney nickel desulfurization to 8-aminovaleric acid. They also confirmed that the acid mp 272-273°C (methyl ester, mp 135-136°C ethyl ester, mp 116-117°C) is 4-acetylamino-2-thiophenecar boxy lie acid as originally stated by Steinkopf and Miiller. The statement of Tirouflet and Chane that the acid obtained upon reduction and acetylation of 5-nitro-2-thiophenecarboxylic acid melts at 272°C must result from some mistake as they give the correct melting point for the methyl ester. 

C,4H2204, melting at 182 5. The formation of this cedrene-dicarboxylic acid serves for the detection of cedrene in essential oils. It is sufficient if the fraction to be examined be oxidised by permanganate or ozone, and the acid obtained (boiling-point at 10 mm. = 200° to 220° C.) be then oxidised further, either by an alkaline solution of bromine or by nitric acid. Even very small proportions of cedrene have definitely led to the obtaining of this acid melting at 182 5° C. 

It can be characterised by its phenyl-urethane, melting at 47° to 48°, or by oxidising its acetic acid solution by means of chromic acid, when it yields hydrocinnamic acid, melting at 49°. 

Cinnamic alcohol forms a phenyl-urethane, melting at 90° to 91°, and a diphenyl-urethane, melting at 97° to 98°. On oxidation it yields cinnamic acid, melting at 133°, and by more thorough oxidation, benzoic acid, melting at 120°. 

By oxidation this alcohol yields perillic aldehyde which forms a semi-carbazone, melting at 199° to 200°, and perillic acid, melting at 130° to 131°. It also yields a naphthyl-urethane, melting at 146° to 147°. 

It is a solid body melting at 112° to 114°, forming exceedingly fine prismatic crystals. It forms a compound with phthalic acid, melting at 140°. 

Pyruvic Acid Compounds.—Lubrzynska and Smedley have recently shown that a number of aldehydes such as heliotropin, anisic aldehyde, benzaldehyde, and cinnamic aldehyde, condense with pyruvic acid in slightly alkaline solution, with the formation of )8-unsaturated-a-ketonic acids. For example, if heliotropin and pyruvic acid in alkaline solution be left standing for about eight days at ordinary temperature, dihydroxy-methylene-benzal-pyruvic acid is formed. This body forms yellow needles, melting at 163° Similarly, anisic aldehyde yields methoxy-benzal-pyruvic acid, melting at 130° and cinnamic aldehyde yields cinnamal-pyruvic acid, melting at 73°. 

It also forms citronellylidene-cyanacetic acid, melting at 137° to 138°. It forms additive compounds with sodium bisulphite, which are similar in characters to the corresponding citral compounds. 

On oxidation it readily yields benzoic acid, melting at 121°. Exposure to the air is sufficient to effect this oxidation. 

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