Benzaldehyde release

Fig. 12 Kinetics of deltamethrin hydrolysis by hCE-1 and hydrolase A. Velocity was measured by the amount of PBald (phenoxy benzaldehyde) released during the reaction. Data symbols) were fit to the Michaelis-Menten equation and the nonlinear regression lines plotted. Each point represents the mean S.D. n = 3). This figure is published with permission (Godin et al. 2006)...

The results found for the volatile release during consumption in this study contradict those found in 2002 by other researchers [20], who observed no change in either ethyl butyrate or benzaldehyde release during consumption of hydroxypropylmethylcellulose (HPMC) at concentrations in solution above c. However, this study differs from that referenced in a number of ways that may explain the different findings (a) In this study the... 

Dissolve I ml. of benzaldehyde and 0-4 ml. of pure acetone in 10 ml. of methylated spirit contained in a conical flask or widemouthed bottle of about 50 ml. capacity. Dilute 2 ml. of 10% aqueous sodium hydroxide solution with 8 ml. of water, and add this dilute alkali solution to the former solution. Shake the mixture vigorously in the securely corked flask for about 10 minutes (releasing the pressure from time to time if necessary) and then allow to stand for 30 minutes, with occasional shaking finally cool in ice-water for a few minutes. During the shaking, the dibenzal -acetone separates at first as a fine emulsion which then rapidly forms pale yellow crystals. Filter at the pump, wash well with water to eliminate traces of alkali, and then drain thoroughly. Recrystallise from hot methylated or rectified spirit. The dibenzal-acetone is obtained as pale yellow crystals, m.p. 112 yield, o 6 g. 

The mechanism for formation of benzaldehyde diethyl acetal which proceeds m two stages is presented m Figure 17 9 The first stage (steps 1-3) involves formation of a hemiacetal m the second stage (steps 4-7) the hemiacetal is converted to the acetal Nucleophilic addition to the carbonyl group characterizes the first stage carbocation chemistry the second The key carbocation intermediate is stabilized by electron release from oxygen... 

An assay method for benzaldehyde involves condensing benzaldehyde with hydroxyl amine hydrochloride to form an oxime. The released hydrochloric acid is then titrated. 

Performing the titration to a potentiometric end point, rather than to a colored end point, has been shown to be the more accurate method. Since other carbonyl containing compounds also react to form the oxime and release hydrochloric acid, this test is not specific for benzaldehyde. 

Not all reactions can be fitted by the Hammett equations or the multiparameter variants. There can be several reasons for this. The most common is that the mechanism of the reaction depends on the nature of the substituent. In a multistep reaction, for example, one step may be rate-determining in the case of electron-withdrawing substituents, but a different step may become rate-limiting when the substituent is electron-releasing. The rate of semicarbazone formation of benzaldehydes, for example, shows a nonlinear Hammett... 

Acetal handle 78 synthesized from Merrifield resin and 4-hydroxy-benzaldehyde was applied to the solid-phase synthesis of carbohydrates and 1-oxacephams (Scheme 41) [90]. For the latter, a 1,3-diol was initially anchored to the support to form a cyclic acetal. A ring opening reaction with DIBAL generated a resin-bound alcohol which was converted to the corresponding triflate for A-alkylation with 4-vinyl-oxyazetidin-2-one. A Lewis acid catalyzed ring closure released 1-oxa-cephams from the support. 

To demonstrate the feasibility of organic synthesis using this support, the authors immobilized a N-Boc protected glycin (22) on the support (Scheme 7.5). After deprotection imine formation readily occurs with an excess of benzaldehyde. The product was then subjected to a Staudinger reaction with phenoxyacetylchlor-ide to yield the polymer supported / -lactam (26) which could be released to give the yS-lactam (27) with TEA in methanol. 

Release of salicylic acid from benzaldehyde disalicyl acetal gives a bell-shaped pH-rate constant profile (Figure 6) analogous to lysozyme-catalysed reactions (Anderson and Fife, 1973). The maximum... 

The dynamic cyanohydrin libraries were generated from equimolar amounts of hve different benzaldehydes (23-27) and acetone cyanohydrin (28) in the presence of triethylamine. This resulted in release of cyanide ion and rapidly provided the cyanohydrin adducts (29-33), all as racemic mixtures of both enantiomers (DCL-D, Scheme 6.6). 

Salicin is an (9-glycoside of a phenol, namely salicyl alcohol. Salicin is a natural antipyretic and analgesic found in willow bark, and is the template from which aspirin (acetylsalicylic acid, see Box 7.13) was developed. Prunasin from cherry laurel is an example of a cyanogenic glycoside, hydrolysis of which leads to release of toxic HCN (see Box 7.7). It is the (9-glucoside of the alcohol mandelonitrile, the trivial name for the cyanohydrin of benzaldehyde. It is the further hydrolysis of mandelonitrile that liberates HCN. 

Isotope effects have also been applied extensively to studies of NAD+/NADP+-linked dehydrogenases. We typically treat these enzymes as systems whose catalytic rates are limited by product release. Nonetheless, Palm clearly demonstrated a primary tritium kinetic isotope effect on lactate dehydrogenase catalysis, a finding that indicated that the hydride transfer step is rate-contributing. Plapp s laboratory later demonstrated that liver alcohol dehydrogenase has an intrinsic /ch//cd isotope effect of 5.2 with ethanol and an intrinsic /ch//cd isotope effect of 3-6-4.3 with benzyl alcohol. Moreover, Klin-man reported the following intrinsic isotope effects in the reduction of p-substituted benzaldehydes by yeast alcohol dehydrogenase kn/ko for p-Br-benzaldehyde = 3.5 kulki) for p-Cl-benzaldehyde = 3.3 kulk for p-H-benzaldehyde = 3.0 kulk for p-CHs-benzaldehyde = 5.4 and kn/ko for p-CHsO-benzaldehyde = 3.4. 

Pinacol rearrangement driven by the release of the ring strain of a cyclobutane ring has been employed in an extremely efficient manner to form cyclopentanone derivatives. Experimentally. the Lewis acid mediated aldol condensation of benzaldehyde with l,2-bis(trimethyl-siloxy)cyclobutcne at —78 C gave the pinacol 1 in its silylated form.35,36 Subsequent treatment of this pinacol with trifluoroacetic acid at room temperature afforded 2-phenyl-cyclopentane-l,3-dione (2) in 97% yield.35,36... 

Acetaldehyde, butylaldehyde, and furfuraldehyde are reported to replace formaldehyde for special purpose Novolak resins (7). However, the formaldehyde Novolak resins are reported to release formaldehyde as the major gaseous product upon heating at 450 °C (26). Formaldehyde is a well-known toxic compound and should be avoided if possible. Benzaldehyde has never been reported as a component for Novolak resins, but has been found to replace formaldehyde in Novolak resin preparations to yield fairly good resist materials. 

An NMR tube (5-mm diameter) is charged with 0.207 g (0.713 mmol) of 2-(diphenylphosphino)benzaldehyde.5 Then a solution of 0.152 g (0.776 mmol) of (CO)5MnH in 1.5 mL of toluene is added via syringe. These operations are conveniently performed in a glove box. The tube is fitted with a septum and is vigorously shaken. A small needle connected to a hood vented oil bubbler is inserted into the septum to release the CO that evolves vigorously. After the CO evolution subsides somewhat, the disappearance of the aldehyde 3H NMR doublet (JHP = 5 Hz, 5 10.5) can be monitored. After 10 h, the aldehyde is consumed. 

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. 

---