Aldehyde odour

Dupical and Scentenal have fresh, floral, aldehydic odours, the others have varying proportions of floral and fruity notes. 

Silicone mbber, like other rubbers that are produced following the peroxide method, can give an aldehyde odour shortly after production. This is caused by traces of... 

As with silicone mbber, ethylene propylene mbber can give an aldehyde odour. Ethylene propylene mbber is highly resistant to water, alkali and dilute acids, and moderately to poorly resistant to hydrocarbons, lipids and concentrated acids. It is resistant to the high temperatures of steam sterilisation. 

HCOOCHjCHj. Colourless liquid with the odour of peach-kernels b.p. 54 C, Prepared by boiling ethanol and methanoic acid in the presence of a little sulphuric acid the product is diluted with water and the insoluble ester separated and distilled. Used as a fumigant and larvicide for dried fruits, tobacco and foodstuffs. It is also used in the synthesis of aldehydes. 

Note cautiously the characteristic odour of acetaldehyde which this solution possesses. Then with the solution carry out the following general tests for aldehydes described on p. 341 Test No. I (SchiflF s reagent). No. 3 (Action of sodium hydroxide). No. 4 (Reduction of ammoniacal silver nitrate). Finally perform the two special tests for acetaldehyde given on p. 344 (Nitroprusside test and the Iodoform reaction). 

Now warm 2-3 drops of acetaldehyde with 3-4 ml. of 10-20 per cent, sodium hydroxide solution, i.e., with excess of concentrated alkali solution. Observe the formation of a yellow aldehyde resin and the attendant peculiar odour. 

Aromatic aldehydes usually have relatively high boiling points, but distil with little or no decomposition. The vapours burn with a smoky flame. They are easily oxidised on standing in the air into the corresponding acids the odours are often pleasant and characteristic. Aromatic aldehydes, by virtue of their high molecular weight, yield... 

Styrene is a colourless mobile liquid with a pleasant smell when pure but with a disagreeable odour due to traces of aldehydes and ketones if allowed to oxidise by exposure to air. It is a solvent for polystyrene and many synthetic rubbers, including SBR, but has only a very limited mutual solubility in water. Table 16.1 shows some of the principal properties of pure styrene. 

Wilh pbeoWaiid iiaphth>l i vcyauaies only li<)uid derivallves were obtained. Mo dljihenyluieohaue was termed. Judging hx Ihe odour, oxidalion with Beckiiiaao s mixture app ars to give rise to an aldehyde. 

Mehrling and Welde first determined if hydro-aromatic ring aldehydes in general gave violet like odours when condensed with acetone, and it was found that in the case of the four following aldehydes only the first yields a body having a violet odour —... 

Lanrinic or duodecylic alcohol has a soft and not very strong hut delicate odour. These alcohols can he used in much greater quantities than the corresponding aldehydes. The latter are only admissible in a... 

Octyl Alcohol.—This is the primary normal alcohol of the formula CH3(CH2)gCH20H. It has an odour recalling that of opoponax, and is useful in the blending of perfumes of this type. It boils at 196° to 197°, and has a specific gravity 0"8278. It yields octyl aldehyde on oxidation, whose naphtho-cinchoninic acid compound melts at 234°. 

The identification of geraniol can be confirmed by its conversion into citral, Cj Hj O, its aldehyde, which has a very characteristic odour and yields well-defined crystalline derivatives. Five parts of the alcohol fraction are shaken with 2-5 parts of chromic acid and four parts of concentrated sulphuric acid dissolved in 100 parts of water. The mixture is warmed in the water-bath for a few minutes, when crude citral separates on the surface of the liquid. This is purified by steam distillation and conversion into its sulphonic acid compound in the... 

It yields a phenyl-urethane, melting at 45". On oxidation it yields an aldehyde having an odour of lemons, which yields a semicarhazone, melting at 135°. 

Eeptylic Aldehyde.—This aldehyde, also known as oenanthylic aldehyde, 18 formed by distilling castor oil under reduced pressure. It is an Oil of powerful fruity odour, boiling at 155°, or at 45° at 10 mm. pressure, and having a specific gravity 0-820, and refractive index 1-4150. It forms an oxime melting at 50°. 

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