Acetaldehyde from propane

Hydroxypentanal (from addition of enolate of acetaldehyde to propanal)... 

The changeover from ROO radicals to HOO radicals and the switch from organic peroxides to HOOH has been shown as temperature is increased in propane VPO (87,141). Tracer experiments have been used to explore product sequences in propane VPO (142—145). Propylene oxide comes exclusively from propylene. Ethylene, acetaldehyde, formaldehyde, methanol, carbon monoxide, and carbon dioxide come from both propane and propylene. Ethanol comes exclusively from propane. 

Examples for necessary process improvements through catalyst research are the development of one-step processes for a number of bulk products like acetaldehyde and acetic acid (from ethane), phenol (from benzene), acrolein (from propane), or allyl alcohol (from acrolein). For example, allyl alcohol, a chemical which is used in the production of plasticizers, flame resistors and fungicides, can be manufactured via gas-phase acetoxylation of propene in the Hoechst [1] or Bayer process [2], isomerization of propene oxide (BASF-Wyandotte), or by technologies involving the alkaline hydrolysis of allyl chloride (Dow and Shell) thereby producing stoichiometric amounts of unavoidable by-products. However, if there is a catalyst... 

Also heterocyclic flavour molecules can be formed from renewable resources. 3,5-Diethyl-1,2,4-trithiolane is an important molecule for onion flavours and can easily be prepared from propanal obtained by biotransformation and hydrogen sulflde (Scheme 13.17). A meat flavour molecule like thialdine [dihydro-2,4,6-trimethyl-l,3,5(4H)-dithiazine] can be prepared from acetaldehyde isolated from molasses and ammonium sulflde (Scheme 13.18). The bacon flavour substance 2,4,6-triisobutyl-5,6-dihydro-4H-l,3,5-dithiazine can be prepared from isovaleraldehyde prepared from essential oils and ammonium sulfide (Scheme 13.19). 

CO elimination from ethanol and 1 -propanol occurred at lower temperature than from acetaldehyde and propanal, thus the latter cannot be intermediates in the reactions of the former. 

When the enolate of one aldehyde (or ketone) adds to the carbonyl group of a different aldehyde or ketone, the result is called a crossed aldol condensation. The compounds used Crossed Aldol in the reaction must be selected carefully, or a mixture of several products will be formed. Condensations Consider the aldol condensation between ethanal (acetaldehyde) and propanal shown below. Either of these reagents can form an enolate ion. Attack by the enolate of ethanal on propanal gives a product different from the one formed by attack of the enolate of propanal on ethanal. Also, self-condensations of ethanal and propanal continue to take place. Depending on the reaction conditions, various proportions of the four possible products result. 

Methyl glyoxal has never been reported in soy sauce or soy bean paste prior to this study. Certain aldehydes (acetaldehyde, n-propanal, 2-methylpropanal, and 3-methylbutanal) were found in soy sauce previously (32). A gas chromatogram of the extract from cysteamine-treated soy sauce and untreated soy sauce are shown in Figures 7 and 8. 

C. A. McDowell and J. B. Farmer, Fifth Symposium (International) on Combustion, p. 453, op. ciL, have shown the formation of peracetic acid as the principal initial product in the photosensitized and thermal oxidation of acetaldehyde. (See also earlier papers of McDowell and Farmer.) J. Grumcr, ibid, p. 447, also showed that, at low O2 content, C2H4, C He, CO, CH4, CH,OH, CHsCHO, and CH,CH2CHO were important products from propane pyrolysis in the range 350 to 475 C. He also found considerable amounts of acetic acid from the oxidation of CHaCHO in mixtures at 130 to 450 C having about 3 per cent O2. Such I0W-O2 mixtures are, of course, ideal for observing sensitized pyrolysis reactions. 

Methylhydrazones act just like protic H—trapping reagentsJ i For example, the methylhydrazone of acetaldehyde 202 undergoes Pd-catalyzed reaction with butadiene to afford linear dimer 203 (1 mol % (Ph3P)4Pd, THF, 110 °C, 24 h, 89%) (Scheme 64). Methylhydrazones derived from propanal, acetone, and methyl ethyl ketone behave similarly (80-86% yield). 

Phenylhydrazones exhibit another mode of reaction (Scheme 65). The reaction of butadiene with the phenylhydrazone of acetaldehyde 204 (1 mol % (Ph3P)4Pd, THF, 110 °C, 24 h) affords a 2 1 mixture of 205 and 206 (86%). A small amount of the protic (H—Y) trapping prodnct was also observed. The formation of 205 can be rationalized by addition of the phenylhydrazone in the fashion of a R (R )C=Y-type electrophile to a palladacycle in an Sgs fashion to 208 followed by hydride transfer to 209. Rednctive elimination conld acconnt for the formation of 205. Thns, 206 could be formed via a similar pathway, by addition of the phenylhydrazone in an rather than fashion. The proposed hydride transfer invoked to rationalize the formation of the observed products offers interesting possibilities and appears worthy of further investigation. Phenylhydrazones derived from propanal, acetone, and methyl ethyl ketone behave similarly (60-95% yield), although the ratio of 205/206 and the proportion of the protic (H—Y-type) trapping product vary. 

Identify the most acidic hydrogens in each of the following molecules. Give the structure of the enolate ion arising from deprotonation, (a) Acetaldehyde (b) propanal (c) acetone (d) 4-heptanone (e) cyclopentanone. 

In the absence of propane, the interaction between methane and zeolite Zn/HBEA yields methylzinc (ZnCHj) and methoxide (ZnOCHj) species and formate fragments, which undergo further conversion into acetaldehyde and acetic acid (Fig. 29D). In the presence of benzene, only the formation of the methoxide ZnOCH is observed, which is apparently not oxidized by oxygen of the defected ZnO structure (Fig. 29E). At 823 K, benzene is methylated by ZnOCHj, yielding methyl-substituted aromatics, namely, toluene and xylenes (Fig. 29F). It was thereby found that methane participated in the methane-propane co-aromatization reaction hy alkylating the aromatic compounds that resulted from propane, as is illustrated hy Scheme 7. 

The first study by the research team was very straightforward PTR-MS was simply employed to monitor the VOC emissions released from ground roasted coffee beans after water at a relatively low temperature of 18°C was added to produce the familiar aroma of coffee we are all familiar with [42]. The following volatile compounds were monitored acetaldehyde, acetone/propanal, methyl ether ketone/methylpropanal, ethyl formate/methyl acetate, acetic acid, methanol, 3-methylbutanal/furan, methyl furan, 5-methylfural, 2,3-butanedione/2-methylbutanal and furfural. 

Moeskops, B. W. M., Steeghs, M. M. L van Swam, K. et al. (2006) Real-time trace gas sensing of ethylene, propanal and acetaldehyde from human skin in vivo. Physiol. Meas. 27, 1187. 

Atkinson et al. (2000) studied the product distribution from the reaction of OH with 2-heptanone, using a combination of detection techniques. In addition to the simple aldehydes, formaldehyde (38% yield), acetaldehyde (15%), propanal (10%), butanal (7%), and pentanal (9%), evidence was found for a number of dicarbonyls and hydroxydicarbonyls, presumably produced following isomerization of the initially... 

At wavelengths of sunlight within the troposphere, only primary processes (I) and (III) are important. Primary processes (II), (IV), (V), (VI), and (Vn) may become significant for photolysis at the shorter wavelengths that are available only in the upper atmosphere. While processes (I), (II), and (VI) are analogous to those observed with acetaldehyde and propanal, process (III) is unique to carbonyl compounds that contain a p-H-atom, an H-atom attached to the third C-atom down-chain from the carbonyl group. This photodecomposition path is often called a Norrish type-II process (Bamford and Norrish, 1935 Davis and Noyes, 1947). The initial enol-form of acetaldehyde formed in (III),... 

Commercial VPO of propane—butane mixtures was in operation at Celanese Chemical Co. plants in Texas and/or Canada from the 1940s to the 1970s. The principal primary products were acetaldehyde, formaldehyde, methanol, and acetone. The process was mn at low hydrocarbon conversion (3—10%) and a pressure in excess of 790 kPa (7.8 atm). These operations were discontinued because of various economic factors, mainly the energy-intensive purification system required to separate the complex product streams. 

It is often said that the property of acidity is manifest only in the presence of a base, and NMR studies of probe molecules became common following studies of amines by Ellis [4] and Maciel [5, 6] and phosphines by Lunsford [7] in the early to mid 80s. More recently, the maturation of variable temperature MAS NMR has permitted the study of reactive probe molecules which are revealing not only in themselves but also in the intermediates and products that they form on the solid acid. We carried out detailed studies of aldol reactions in zeolites beginning with the early 1993 report of the synthesis of crotonaldehyde from acetaldehyde in HZSM-5 [8] and continuing through investigations of acetone, cyclopentanone [9] and propanal [10], The formation of mesityl oxide 1, from dimerization and dehydration of... 

Several of the lower molecular weight aliphatic compounds, in a mixture, are part of the roasted coffee aroma. A nine-compound mixture with roasted coffee aroma contained isopentane, n-hexane, acetaldehyde, dimethyl sulfide, propanal, isobutanal, isopentanal, methanol, and 2-methylfuran.20 In addition, the freshness of aroma and taste has been correlated with 2-methylpropanal and diacetyl. When the concentration of these falls off, so does the taste.21 Other aliphatic compounds that are steadily lost from ground roasted coffee, unless it is vacuum packaged, include methyl formate, methyl acetate, methyl thioacetate, and acetone.22 The concentrations in roast coffee for four compounds whose contribution to the fresh flavor have long been known are dimethyl sulfide (4 ppm), methyl formate (12 ppm), isobutanal (20 ppm), and diacetyl (40 ppm). The taste thresholds are 0.1, 0.5, 0.5, and 1.0 ppm, respectively, in the brew made with 5 g coffee per 100 ml water.15... 

Because hydrogen can easily be removed from a reaction stream, many dehydrogenations have been studied. These include dehydrogenation of methane to carbon,326 ethane to ethene,327,328 propane to propene,329 n-butane to butenes,330 isobutane to isobutene,331,332 cyclohexane to benzene,332-334 meth-ylcyclohexane to toluene 335 n-heptane to toluene,336 methanol to formaldehyde,330 and ethanol to acetaldehyde.337... 

X-ray structure analyses of Rh(COCH3)(I)2(dppp) (14) and [Rh(I I)(I)(//-I)(dppp)]2 (15), where dppp l,3-bis(diphenylphosphino) propane, were reported. Unsaturated complex (14) possesses a distorted five-coordinate geometry that is intermediate between sbp and tbp structures.69 Under CO pressure, the rhodium/ionic-iodide system catalyzes either the reductive carbonylation of methyl formate into acetaldehyde or its homologation into methyl acetate. By using labeled methyl formate (H13C02CH3) it was shown that the carbonyl group of acetaldehyde or methyl acetate does not result from that of methyl formate.70... 

A few plants have been built to oxidize normal paraffins such as propane and butane. Air and paraffin are charged to a tubular furnace at a temperature of about 700 R Acetaldehyde yields from butane are about 30—35%. 

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