Aldehyde smell

The functional group names can be used in characterizing and describing the odours of many perfumes and some of the essential oils. Aldehydic smelling oils are due to compounds with functional groups called aldehydes, and sweet and fruity smelling oils are due to compounds with functional groups called esters. 

Aldehydes h ive very powerful aromas and widespread use in the perfumery industry. Chanjel No. 5 is described as having an aldehydic smell. The aldehydes used in perfumery are not the terpene derivatives but are usually synthetic fatty aldehydes. 

METHOD 2 [89]--1M MDA or benzedrine and 1M benzaldehyde is dissolved in 95% ethanol (Everclear), stirred, the solvent removed by distillation then the oil vacuum distilled to give 95% yellow oil which is a Schiff base intermediate. 1M of this intermediate, plus 1M iodomethane, is sealed in a pipe bomb that s dumped in boiling water for 5 hours giving an orangy-red heavy oil. The oil is taken up in methanol, 1/8 its volume of dH20 is added and the solution refluxed for 30 minutes. Next, an equal volume of water is added and the whole solution boiled openly until no more odor of benzaldehyde is detected (smells like almond extract). The solution is acidified with acetic acid, washed with ether (discard ether), the MDMA or meth freebase liberated with NaOH and extracted with ether to afford a yield of 90% for meth and 65% for MDMA. That s not a bad conversion but what s with having to use benzaldehyde (a List chemical) Strike wonders if another aldehyde can substitute. 

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. 

Chloral hydrate (Noctec, Somnos) was developed in the late 1800s and is still used as a sedative-hypnotic agent. It is a hydrated aldehyde with a disagreeable smell and taste that is rapidly reduced in vivo to trichloroethanol, which is considered to be the active metabohte. It produces a high incidence of gastric irritation and allergic responses, occasionally causes cardiac arrhythmias, and is unreliable in patients with liver damage. 

Phenol aldehydes are generally pleasant-smelling products. Some of them are particularly important as fragrance and flavor materials. Anisaldehyde and certain derivatives of protocatechu aldehyde (3,4-dihydroxybenzaldehyde) are well-known representatives. The monomethyl ether of protocatechu aldehyde, vanillin, is perhaps the most widely used flavor material. Other important derivatives of this aldehyde are veratraldehyde (dimethyl ether) and heliotropin (formaldehyde acetal derivative) they are not only used as fragrance and flavor substances, but also are intermediates in many industrial processes. 

Many aldehydes are particularly fragrant. A number of flowers, for example, owe their pleasant odor to the presence of simple aldehydes. The smells of lemons, cinnamon, and almonds are due to the aldehydes citral, cinnamalde-hyde, and benzaldehyde, respectively. The structures of these three aldehydes are shown in Figure 12.21. The aldehyde vanillin, introduced at the beginning of this chapter, is the key flavoring molecule derived from the vanilla orchid. You may have noticed that vanilla seed pods and vanilla extract are fairly expensive. Imitation vanilla flavoring is less expensive because it is merely a solution of the compound vanillin, which is economically synthesized from the waste chemicals of the wood pulp industry. Imitation vanilla does not taste the same as natural vanilla extract, however, because in addition to vanillin many other flavorful molecules contribute to the complex taste of natural vanilla. Many books made in the days before acid-free paper smell of vanilla because of the vanillin formed and released as the paper ages, a process that is accelerated by the acids the paper contains. 

Odor masking does little or nothing to control malodors it merely covers them up. Many materials used in masking odors are aldehydes, which are very chemically reactive and usually comprise the top note of a fragrance. Odor masking is used in many areas of household, industrial, and institutional use via products that mask such malodors as pel smells, smoke, cooking, and numerous other odors. The forms by which masking is executed vary, and can be solid, liquid, and aerosol. 

This is extracted from the peel of the fruit of Citrus limomm by pressure, either manual or mechanical. 11 is a pale yellow, sometimes slightly greenish liquid with the smell of fresh lemons in time it resinifies, decolorises and acquires a special resinous odour. It consists mostly (about 90%) of limonene and contains also small proportions of other terpenes, citral (which determines its value, as it contributes largely to the aroma) and other aldehydes and traces of esters. 

Comparison of (5) with (6a) + (6b) (heated in separate tubes but smelled together) should show similarly the extent to which furfural can affect a normal aldehyde. Comparison of (7) with (8a) + (8b) and of (9) with (10a) + (10b) should show little difference because of considerable survival of volatile aldehydes in presence of a blocking Group 2 aldehyde (from ile). 

Polyurethanes (PU) The odor of many polyurethanes is caused by fishy smelling low molecular weight amines, mostly methylamines like trimethylamine, degradation products of the amine catalysts used during production. In some cases after evaporation of the fishy smelling amines, other odor qualities remain. One noticeable odor of PU samples was earthy, nutty, which can often be attributed to substituted pyrazines, formed by condensation of two a-aminoketones, subsequent oxidation or alkylation by aldehydes. One example is 2-ethyl-3,5-dimethylpyrazine (Mayer and Breuer, 2006). 

It is a known fact that many freshly printed books and journals have strong odor. In a particularly severe case, school children complained that they were irritated when they touched a schoolbook with a PVC cover. To find out the reasons, the book was conditioned for 24h and put into a 23.5-1 chamber with open pages at T = 23 °C, RH = 45% and N = 1.0h"1. Sampling was performed after 24h and 48h. As shown in Table 15.3, very high emissions of aromatic hydrocarbons, glycols and other compounds were observed. In addition, a chamber test carried out on issue 4/96 of Indoor Air journal showed that it had an unpleasant smell. The main components detected in the chamber air were formaldehyde (335 (tg/m3), hexanal (15 xg/m3), toluene (123 ( Lg/tn3) and aliphatic hydrocarbons (>C10) (100—150 (xg/ m3). Higher aliphatic aldehydes (C7-C11) appeared in concentrations <10 tg/rn3. 

Organic components of polishes are widespread. Thus most products emit complex VOC mixtures that may consist of alkanes, various alcohols, acetates, C2-C4-benzenes, terpenes and derivatives of naphthalene. This is illustrated by the range of compounds emitted by a furniture polish (Figure 15.2b) and a shoe polish (Figure 15.2c). Many modern floor waxes are based on natural ingredients like alkyd resins. On oxidative degradation of unsaturated fatty acids, volatile aliphatic aldehydes (C5-C11) with unpleasant smell (Ruth, 1986) are formed and the emission rates may remain at high levels over months and even years (Salthammer, 1999). 

The smell of Galaxolide has become very much associated with its use as a major component of many washing powders and fabric conditioners and its use here in conjunction with a high proportion of aldehydes may have been used deliberately to give the character of freshly washed white linen—or perhaps it was the fragrance that inspired the name. 

The uses of vanillin in international perfumery are many. In aldehydic perfumes, vanillin provides the powdery impression given by the background smell, usually up to 2% in the perfume concentrate. In fruity notes, vanillin enhances the various fruity constituents (0.1—0.5% in pears up to 2% in peaches) for instance, a peach note is not fully peach without vanillin. When vanillin is combined with some floral notes, such as heliotrope and orchid, which actually contain strong vanilla impressions, amounts of 2—5% are possible. However, with notes such as rose, orange flower, and jonquil, the addition of 0.1—2% vanillin can bring warmth and elegance. In woody families such as fougiire and chypre, and also in spicy perfumes, the harsh impression also needs the fine, smooth aroma provided by vanillin traces. 

Hexenal (leaf aldehyde) is a constituent responsible for the smell of green leafs, ( )-2-octenal a main component of the aroma of raw potatoes ( )-2-nonenal is the organoleptic main constituent of the smell of cucumbers and is found in carot root oil, tomatoes, beef and raspberries 158). ( )-2-Decenal and ( )-2-dodecenal are components of some essential oils, ( )-2-tridecenal is responsible for the bug-like smell of coriander seed oil1S8). 

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