Burnt almond

The influence of structure on the acute toxicity of nitriles can be used in a lecture to illustrate the fundamental structure-hazard link. Many chemists who have participated in an organic chemistry laboratory section will remember the warning that the aroma of burnt almonds may indicate that cyanide has been released. An opportunity exists for the laboratory instructor to explain where and how cyanide evolved and that it is an acutely dangerous chemical.. This example that can be incorporated into the first-day lab overview is to include a discussion of the source and toxicity of nitriles to humans. Nitriles are ubiquitous in a synthetic laboratory and can liberate cyanide under certain circumstance. The structural features that are associated with a greater chance of cyanide being liberated from a nitrile have been studied and reported (14). 

HCN has a faint, bitter, burnt almond-like odor that some people are unable to detect owing to a genetic trait. The volatile compound has been used as inhalation rodenticide and human poison. Cyanide ions interfere with iron-containing respiratory enzymes. 

Wood ashes.—The ash of wood, not coal, contains about 30 per cent, of potassium carbonate. Prior to the exploitation of the Stassfurt salts about the middle of the nineteenth century, the chief source of potash was wood ashes, and the process is still used in certain localities where wood-fuel is employed and where much waste wood is available—e.g. in some parts of Canada, United States, Russia, Spain, etc. The ash of trees, hedge-cuttings, sawdust, etc., can be made to yield potash.5 In the Caucasus, the sunflower is grown on waste land for the sake of its seed. The stalks, leaves, etc., are a by-product and are burnt the ash is used as a source of potash. Nearly 7000 tons per annum of crude potash from this source were exported from Novorossik in Russia. The residues in the manufacture of olive oil and almond shells are also stated by G. l Abate to be exceptionally rich in potash salts F. W. F. Day claims that the roots of the water hyacinth (eiehornia crassipes) have... 

F Sweet-caramellic, warm O Burnt, caramel-like, slightly meaty F in beer Almonds, burnt/phenolic, pyrazole... 

Tests on a number of these small units revealed that the ozone concentration in the room was less than 0.01 p.p.m. by weight. There is ample evidence that various food odors, such as from fish, onions, acrolin from burnt fat, and tobacco as well as body odors can be oxidized by ozone. This is substantiated by many reports in the literature (4,13-15j 30y SI). Tests made in the laboratory with various unsaturated organic compounds such as indole and skatole (fecal odor), allyl sulfide (garlic odor), and methyl thiocyanate (unpleasant odor of almonds) showed them to be readily oxidized, as evidenced by lack of odor. Saturated compounds such as butyric and valeric acids were not oxidized under the same conditions. Special fixures with ultraviolet lamps producing a controlled amount of ozone are used in animal hospitals and kennels for prevention of cross infection and for the oxidation of animal and fecal odors. 

Furans furfural with its caramel, burnt, ethereal, almond character, is the most prominent sugar degradation product. 2-Methyl-5-ethyl-4-hydroxy-dihydro-furan-3(2H)-one has a strong, sweet, caramel, bread note. 

The flavor of the tautomer mixture is perceived as burnt sugar, maple, cereal, chicory (Chemisis, 1978). The odor threshold reported by Semmelroch et al. (1995) was 1.15 ppm in water with a caramel-like quality. The odor threshold in air given by Blank et al. (1992b) was 0.5-1.5 p,g/m3. A flavor threshold of 21 ppb was reported by Huber (1992). By their enantioselective separation (see in 1.100), Bruche et al. (1995) determined that only one isomer of the less abundant tautomer 1.101b had a very intensive roasted almonds odor, the other isomer being less intensive of the two other tautomers, one is odorless, and the other reminiscent of the odorant 1.101b, is nearly odorless. Therefore ca 85 % of the mixture have no influence on the aroma. 

Nitrobenzene is pale yellow liquid with a bitter almond flavor. It is insoluble in water with a density larger than water, and soluble in alcohol, ether, benzene and oil. In the case of fire, it will be burnt and explode after the heat at high temperature, and can reacts violently with nitric acid. The relative density is 1.205 (15 °C) with melting point of 5.7 °C, boiling point of 210.9 °C, flash point of 87.78 °C, ignition point of 482.22 °C, vapor density of 4.25 and vapor pressure of 0.13 kPa (1 mmHg, 44.4 °C). 

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