With //-heptane

A number of laboratory tests are used to predict chemical stabihty. The amount of existent gum in a gasoline is determined by ASTM D381. This method involves evaporating a sample by a jet of heated air. The residue is weighed, solubles are extracted with / -heptane, and the sample is reweighed. 

A weigh tank containing chlorosulfonic acid needed to be cleaned to remove salt deposits. The salt deposits precipitated from the material and occasionally plugged the downstream control valve. Since the material was water reactive, heptane was chosen to clean the vessel. Chemists had not anticipated the material would be reactive with heptane. While cleaning the vessel the pressure... 

Dissolved in water and extracted with -heptane to remove ethylene glycol dimethacrylate (checked by gas-liquid chromatography and by NMR) and distilled twice under reduced pressure [Strop, Mikes and Kalal J Phys Chem 80 694 1 976]. 

The oxazaborolidines are easily prepared by heating ephedrine with borane dimethyl sulfide or the appropriate boronate ester. The aluminum reagent C is obtained by mixing ephedrine and trimethylaluminum. Borolidinc A is superior to its methyl derivative B and to the aluminum analog C. The diastereomeric borolidine obtained from borane and (S,S)-pseu-doephedrine failed to show any cnantioselectivity25. A variety of aromatic aldehydes can be enantioselectively alkylated in the presence of A, however, with heptanal the enantioselectivity is poor25. 

Diglycidyl ether of bisphenol A (DGEBA, MW 340 Da) and 4,4 -dihydroxy-diphenylmethane (DHDPM, MW 200 Da) were analysed by SEC-MALS [784]. DGEBA and DHDPM are the basic oligomers of epoxy resins and phenol-formaldehyde condensates, respectively, which are widely used in the electronic and automotive industries. Excellent reproducibility ( 1 %) and good accuracy (better than 10%) were observed. SEC has also been used for the determination of mineral oil in extended elastomers [785] and in PS [178]. With heptane containing 0.05% isopropanol as the mobile phase, mineral oil is completely unretained and elutes before the solvent via SEC all other components in a PS extract are retained on silica and elute after the solvent peak. 

If the performance of a column is no longer satisfactory it can sometimes be reconditioned by washing with a suitable solvent, or series of solvents. Some bonded phase columns, C-18 for instance, tend to collect non-polar impurities, which can sometimes be removed by washing the column with a non-polar solvent, eg heptane. Assuming the mobile phase normally used with the column is CH3OH/H2O 50 50, we cannot wash directly with heptane because of miscibility problems, we have to get to heptane via a miscible solvent or series of solvents. 

Szathmary and Luhmann [50] described a sensitive and automated gas chromatographic method for the determination of miconazole in plasma samples. Plasma was mixed with internal standard l-[2,4-dichloro-2-(2,3,4-trichlorobenzyloxy) phenethyl]imidazole and 0.1 M sodium hydroxide and extracted with heptane-isoamyl alcohol (197 3) and the drug was back-extracted with 0.05 M sulfuric acid. The aqueous phase was adjusted to pH 10 and extracted with an identical organic phase, which was evaporated to dryness. The residue was dissolved in isopropanol and subjected to gas chromatography on a column (12 m x 0.2 mm) of OV-1 (0.1 pm) at 265 °C, with nitrogen phosphorous detection. Recovery of miconazole was 85% and the calibration graph was rectilinear for 0.25 250 ng/mL. 

Test solution. Dissolve 0.25 g of the substance to be examined in the internal standard solution and dilute to 5.0 mL with the same solvent. Dilute 1.0 mL of the solution to 10 mL with heptane. 

The slurry was filtered and the solid was washed with heptane (200 mL). The off-white solid was dried in vacuo to give 89 g (93% ee, >99% cp) of the desired alcohol. 

The slurry was filtered and the solid washed with heptane (25 mL). 

The content of the products of lipid peroxidation (LPO) was determined after 1 h of incubation of the cells in a buffer A at 37 °C. Aliquot of cell suspension (100 pg protein) was treated with heptane/isopropyl alcohol mixture at the ratio of 1 1. The content of Schiff bases in heptane phase was analyzed on fluorimeter RF-510, Shimadzu (Japan) at iexit = 360 nm and Xgms = 420 nm (Kolesova et al., 1984). The content of diene conjugates was determined by spectrophotometry (Gavrilov et al., 1988) at the wavelength of X = 245 nm using spectrophotometer Scinco (Germany). 

Feces from injected (7.9 mg/kg) male rats were collected for one week and extracted with acetone yielding about 50% of the dose. Fish were treated with 5 ppb of the compound in water for 48 hr and then held in clean water for 11 days at the end of which they were extracted whole with organic solvents. Recovery of the compound applied to fish was 74.3%. Chromatographs (0.25 mm Silica gel GF-254) were developed with heptane twice. The figure shows relative abundance of metabolites in the two species. PC is photo-cis-chlordane. 

Lieflander and Stbber (218) treated Aerosil and other silicas with solutions of triisobutyl aluminum, Al(C4Hg)g, in heptane. After thorough washing with heptane, about 5.7 /itmole/m of aluminum remained on the surface. This figure agrees well with other reactions of the silanol groups. The reaction and subsequent hydrolysis were formulated as... 

With -heptane feed, a high-temperature benzene peak appeared apart from the low-temperature toluene peak. This also appeared with toluene, but was absent with benzene feed. Benzene must have been formed, therefore, after ring closure via toluene bonded to the surface through its methyl group. This could be removed only by demethylation 62e). The benzene peak gradually decreased with more and more sintered Pt/Al203 catalysts 62d). 

Figure 13.31 Hydroprocessing octadecane 2% feed diluted with heptane) over biflinctional catalysts (contains Pt) with TON and MTT framework types at230°C, 450kPa, H2 HCBN = 13 and varying flow rates [28],...

Separation of catalysts from high-value products such as fine chemicals or pharmaceuticals is often accomplished by precipitating the catalyst from the product solution. Recycling of these catalysts is feasible, provided that they do not decompose. In industry, catalyst recovery by means of catalyst precipitation is applied only in relatively small batch processes. An example of such a process is the production of (—)-menthol (id) in which an Rh-BINAP isomerization catalyst converts the allylic amine substrate into (R)-citronellal (after hydrolysis of the enamine) in high yield (99%) and with high enantioselectivity (98.5% ee). After distillation of the solvent (THF) and product, the catalyst is recovered from the residue by precipitation with -heptane. 

Cross-aldol Condensation of Benzaldehyde with Heptanal on Basic Catalysts (236)... 

The polypropylene so obtained has a high molecular weight and is crystalline.The proportion of isotactic polymer, determined by extracting with heptane for 10 h in a Soxh-let apparatus, is 98.5%. Isotactic polypropylene shows similar solubility behavior to polyethylene, but has a higher melting point (crystalline melting range 165-171 °C). 

A 50-mL sample of distillate fuel is immersed in a 300°F (149°C) oil bath for 90 minutes. After removalfrom the bath and cooling to room temperature, the color of the fuel is measured and compared to the initial color. The fuel is then vacuum filtered through two 1 Whatman filter pads and rinsed with heptane. The color of the pad is compared to a standard color chart and rated. The color of the pad may also be measured by a light reflectance meter. 

Ruggedness test for the determination of water in fertilizers by total distillation with heptane [12]... 

The first pyrazolo[l,5-c]pyrimidine derivative (191) was prepared by condensing thiosemicarbazide with heptane-2,4,6-trione in the presence of perhydroacetic acid (72CB388). This reaction was adopted for the preparation of derivatives of 191 (X = O, NH), and later used to synthesize other pyrazolo[ 1,5-c] pyrimidines (71GEP2131790). 

After stirring for 2 h, the pressure was released and the solvent was evaporated in a slow stream of nitrogen gas. The residue was extracted with heptane (3mL) and the resulting suspension filtered through a syringe filter. The filtrate was directly analyzed by GC and chiral HPLC to determine the conversion and enantiomeric excess (for analytical procedures and data, see ref. [1]). 

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