Dean-Stark method

Instead of using the Dean-Stark apparanis, the reacdon can be carried out at reflux using MeNH-vCl/AcOK/MeOH with HCfOMe, as a water scavenger, A wide variety of nitroalkenes can be prepared in good yields by this method fEq, 3,35, " ... 

Mix 5.5 g 3,4,5-trimethoxybenzaldehyde (or analog), 2.5 g NH4 Acetate, 25 ml nitroethane (or equimolar amount nitromethane for the analog), 25 ml benzene and reflux about twenty hours water being removed with a Dean-Stark tube. Cool and wash with 2X25 ml water, 2X25 ml saturated NaHS03 and 2X25 ml water and dry and evaporate in vacuum the benzene to get (I). Reduce the nitropropene (or nitrostyrene) by any method such as follows To a stirred suspension of 3 g lithium aluminum hydride in 50 ml tetrahydrofuran, add 4.4 g (I) in 50 ml tetrahydrofuran and reflux one hour. Cool in ice bath and treat slowly with wet tetrahydrofuran... 

The weak nucleophilic nature of polynitroaliphatic alcohols means that reactions often need to be catalyzed by Brpnsted acids or Lewis acids. The following methods are commonly used for the esterification of polynitroaliphatic alcohols (1) heating a solution of the alcohol and acid in the presence of sulfuric acid with Dean-Stark removal of water ° (2) using the acid chloride or anhydride in the presence of aluminium chloride " (3) reacting the acid and alcohol... 

Cyclic acetals are useful and common protecting groups for aldehydes and ketones, especially during the course of a total synthesis [8]. The successful synthesis of acetals frequently relies on the removal of water, a by-product of the reaction between the carbonyl compound and the corresponding diol. A Dean-Stark trap is often used for the removal of water as an azeotrope with benzene, but this method is not suitable for small-scale reactions. In addition, the highly carcinogenic nature of benzene makes it an undesirable solvent. Many of the reported catalysts for acetal synthesis such as p-toluenesulfonic acid and boron trifluoride etherate are toxic and corrosive. 

We developed a method for the synthesis of a variety of cyclic acetals that utilizes bismuth triflate as a catalyst and does not require the use of a Dean-Stark trap for removal of water [102]. In this method, an aldehyde or ketone is treated with 1,2-bis (trimethylsiloxy)ethane in the presence of bismuth triflate. A comparison study using o-chlorobenzaldehyde showed that with ethylene glycol a low conversion to the dioxolane was observed after 2 h whereas the use of the 1,2-bis(trimethylsiloxy) ethane afforded the corresponding dioxolane in good yields. (Scheme 9). 

A 10 gram sample was placed in a 200 ml round bottom flask and 100 ml of distilled water added. A Dean-Stark trap and condenser were used and the mixture was brought to a boil. The steam distilled oil was measured after four hours versus control mixtures. In order to measure surface oil on the spray-dried powders, the powder was first washed with a solvent (ethyl ether or hexane) then oil retentions were run by the steam distillation method illustrated above. Differences in oil volume for solvent washed versus non-washed were attributed to surface oil on the spray-dried powders. 

Macrolides. Steliou, Hanessian, and co-workers- have prepared lactones and lactams in moderate to excellent yield by treatment of ro-hydroxy or ru-amino carboxylic acids with catalytic amounts of di-r -butyltin oxide in refluxing mesitylcne or xylene in a Dean-Stark apparatus for 12 24 hours. The method has the advantage of high dilution, since the tin reagent is regenerated continuously. As expected, yields arc low for medium-sized rings. 

Secondary amines react with ketones that contain an H atom in the a-position through an addition and subsequent El elimination to form enamines (Figure 9.29). In order for enamines to be formed at all in the way indicated, one must add an acid catalyst. In order for them to be formed completely, the released water must be removed (e.g. azeotropically). The method of choice for preparing enamines is therefore to heat a solution of the carbonyl compound, the amine, and a catalytic amount of toluenesulfonic acid in cyclohexane to reflux in an apparatus connected to a Dean-Stark trap. Did someone say Le Chateher ... 

For the purposes of this method, a soil/sediment sample is defined as a portion of wet soil/sediment which does not contain oil, but which may contain other solids such as stones, vegetation, etc. The sample should not contain an obvious liquid phase (see Section 8.4). A 10 g aliquot of the soil/sediment sample is spiked with the internal standard solution and extracted with toluene in a combination of a Soxhlet extractor and a Dean Stark water separator (SDS). 

For the purposes of this method, a chemical waste sample includes sample matrices of oils, stillbottoms, oily sludge, oil-laced soil, and surface water heavily contaminated with the matrices listed above (see Section 8.2). Internal standards are added in the concentrations listed in Table 4 to a 1 or 10 g aliquot of chemical waste. Wet fuel oil and oily sludge samples, showing signs of water, are spiked with the internal standard solution, fitted with a reflux condenser and a Dean Stark water separator to remove the water, and extracted with toluene. Stillbottom samples are spiked with the internal standard solution, refluxed with toluene, and filtered. 

The methods reported for the preparation of the oxazaborolidine include the reaction of diphenylprolinol with methylboronic acid 1) in toluene at 23°C for 1.5 hr with 4 A molecular sieves present and 2) in toluene at reflux for 3 hr using a Dean-Stark trap, bolh followed by evaporation of solvent and molecular distillation (0.1 mm, 170°C).5( An alternate method involved heating a toluene solution of 2-naphthylprolinol and methylboronic acid at reflux for 10 hr using a Soxhlet extractor containing 4 A molecular sieves.5 These methods afforded erratic results. The submitters therefore developed an alternate synthesis. 

Method A mixture of benzyl alcohol (100 mL), toluene (200 mL), H-Thr-OH (11.9 g, 0.1 mol), and TosOH H2O (24.7 g) was refluxed using a Dean-Stark trap until no more H2O was collected (18-22 h). The mixture was chilled, diluted with EtOAc (150 mL), and extracted with sufficient cold 0.5 M Na2C03 to bring the aqueous phase to pH 9. The combined organic phases were washed with H2O and dried (MgS04). Oxalic acid dihydrate (12 g, 0.1 mol) in MeOH (60 mL) was added and the hemioxalate salt was collected by filtration then washed with cold EtOH to give colorless crystals yield 9.1 g (23%) mp 165-167 °C [a]o -44.6 (c 1.2, MeOH). 

According to Eq. (11), Confalone has presented a new method of generation of azomethine ylides through the condensation of N-substituted ot-amino esters with aldehydes (83JOC2994 84JA7175). Thus, 5-formylmethyldibenzo-[a.d]tropylidene or o-(allyloxy)benzaldehyde is heated with ethyl sarcosinate or methyl prolinate under reflux in toluene. The water formed is continuously driven off with the aid of a Dean-Stark trap. The ester-stabilized azomethine ylide 77 or 78 quantitatively generated is trapped in an intramolecular fashion. 

Oil and Water Content with Solids. Many methods determine the relative amounts of water and oil in emulsions. Because many emulsions of interest to the oil industry also contain solids, determination of the solids content is also important (22, 23). The Institute of Petroleum (IP), the American Petroleum Institute (API), and the American Society for Testing and Materials (ASTM) have developed standard methods for these determinations, as have most organizations or laboratories where these determinations are routinely performed (24-28). These methods are all some modification of the Dean-Stark procedure, in which the sample is placed in a porous thimble and refluxed with a suitable organic solvent. 

To effectively monitor the separation efficiency of the particular treatment equipment, two specific methods are employed centrifugation (discussed briefly under Testing Procedures ) and the Dean-Stark analysis. The Dean-Stark analysis determines the fractional composition of oil-hydrocarbon, water, and solids of an emulsion stream by using a distillation process. Its results for heavy-oil emulsions are generally more reliable than those obtained by centrifugation however, the results of centrifugation are... 

Sample Number Dean-Stark Centrifugation Analysis Method % Difference ... 

Paraformaldehyde Method. 2,2,4,4-Tetramethyl-1,3-cyclobutanediol. A 2-liter, three-necked flask was fitted with a glass stirrer, thermometer, and Dean-Stark trap which was filled with distilled cyclohexane and attached to a water-cooled condenser. In the flask were placed 216 grams (1.5 moles) of 2,2,4,4-tetramethyl-l,3-cyclobutanediol (1 to 1 cis-/trans- mixture), 52.2 grams (1.65 moles, if 95% pure) of paraformaldehyde, 1200 ml. of distilled cyclohexane, and 0.20 gram of methanedisulfonic acid in a 10 to 25% aqueous solution. (The catalyst solution had been treated with Darco G-60 to remove all color.) While this mixture was stirred at 60° C., the paraformaldehyde depolymerized to formaldehyde, which reacted with the diol. Complete reaction of these two components was indicated when they had gone into solution. This required about 1 hour. 

Paquette found this method satisfactory for the conversion of 2-chloro-l-formyl-1-cyclohexene (4) into 2-chloro-1-cyclohexene-1-carbonitrile (7), Formation of the hydrazone 1.5) was curried out by refluxing the reuctunis for 16 hrs. under a Dean Stark wulcr sepimitor of the design described by Nuteison and Uottfried, ... 

This variation of the Knoevenagel reaction will give somewhat higher yields of product than the preceding method. The reason for the higher yield is the use in this method of toluene as solvent, and the placement of a Dean Stark trap above the flask to remove water from the mixture as it is formed. Removal of water favors the formation of greater quantities of nitroalkene. 

The most common method to prepare a ketal is to treat the carbonyl compound with ethylene glycol and an acid at reflux with a solvent that will azeotrope water using a Dean-Stark trap. For substrates that can not tolerate high temperatures, a dehydrating agent such as trimethylorthoformate is often used to scavenge the water. 

Allyl alcohol, TsOH, CHCI3, reflux, inverse Dean Stark trap, 72-98% yield. The method was developed for p,7-unsaturated esters. ... 

Soil, sediments, and other solid sample matrices (congener specific) Filtered and homogenized extracted using Soxhiet/Dean-Stark extractor cleanup using sulfuric acid and chromatography HRGC/HRMS See Table 7-1 No data EPA 1999k (method 1668)... 

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