Analysis infrared

The stretching vibrations of common functional groups tend to fall within distinct regions of the IR spectrum [25] as described in the following. 

Type of C-H bond Example Bond strength (kcal moT ) IR frequency (cm ) 

C-C triple and double bond stretching frequencies The bond is not considered 

Like the CsC bond, the C=C bond stretch is not a very reliable functional group. However, it is also characterized by a strong force constant and because of this, one can enhance the intensity of this stretching frequency, this absorption can provide useful and reliable information. In simple system, the terminal carbon-carbon double bond (C=CH2) is the most reliable and easiest to identify since the absorption is of moderate intensity at 1600-1675 cm .  

C-0 single bond stretching frequency C-O single bond displays stretching bands in the region 1200-1100 cm . The bands are generally strong and broad. 

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Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

The deterrnination of impurities in the hehum-group gases is also accompHshed by physical analytical methods and by conventional techniques for measuring the impurity in question (93), eg, galvanic sensors for oxygen, nondispersive infrared analysis for carbon dioxide, and electrolytic hygrometers for water. 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

D. A. Bums and E. W. Ciurczak, eds.. Handbook of Near-Infrared Analysis, Marcel Dekker, Inc., New York, 1992. 

Assay of hydrogen cyanide can be done by specific gravity or silver nitrate titration. Sulfur dioxide in hydrogen cyanide can be deterrnined by infrared analysis or by reaction of excess standard iodine solution and titration, using standard sodium thiosulfate or by measurement of total acidity by... 

The most common methods for monitoring solid phase reacdons udlized in normal research laboratories are Infrared analysis of resin... 

The time necessary for completion of the reaction may vary from 0.5 to 4 hours, depending on the actual activity of the alumina. The progress of conversion should be monitored by infrared analysis of a concentrated sample of the solution. Stirring should be continued for 15 minutes after the nitroso band at 1540 cm. has disappeared. A strong diazo band at about 2100 cm. will then be present. The carbonyl band at 1750 cm. initially due to nitrosocarbamate, will usually not disappear completely during the reaction, because some diethyl carbonate is formed in addition to carbon dioxide and ethanol. Diethyl carbonate is removed during the work-up procedure. 

This method is particularly applicable to the more reactive benzyl halides which are easily hydrolyzed in the aqueous media usually employed for the metathetical reaction with alkali cyanides. For example, anisyl chloride treated with sodium cyanide in aqueous dioxane gives, as a by-product, 5-10% of anisyl alcohol as determined by infrared analysis. The use of anhydrous acetone not only prevents hydrolysis to the alcohol but also decreases the formation of isonitriles. This method was also applied successfully by the submitters to the preparation of -chlo-rophenylacetonitrile in 74% yield. 

Table 10.17 Compounds detectable by portable infrared analysis (MIRAN 1A)...

Estrone methyl ether (100 g, 0.35 mole) is mixed with 100 ml of absolute ethanol, 100 ml of benzene and 200 ml of triethyl orthoformate. Concentrated sulfuric acid (1.55 ml) is added and the mixture is stirred at room temperature for 2 hr. The mixture is then made alkaline by the addition of excess tetra-methylguanidine (ca. 4 ml) and the organic solvents are removed. The residue is dissolved in heptane and the solution is filtered through Celite to prevent emulsions in the following extraction. The solution is then washed threetimes with 500 ml of 10 % sodium hydroxide solution in methanol to remove excess triethyl orthoformate, which would interfere with the Birch reduction solvent system. The heptane solution is dried over sodium sulfate and the solvent is removed. The residue is satisfactory for the Birch reduction step. Infrared analysis shows that the material contains 1.3-1.5% of estrone methyl ether. The pure ketal may be obtained by crystallization from anhydrous ethanol, mp 99-100°. Acidification of the methanolic sodium hydroxide washes affords 10-12 g of recovered estrone methyl ether. 

The reaction mixture was removed from the vessel and distilled at a pressure of 30-60 mm, and a bath temperature of 30°C to 50°C until the methanol had all been removed. The extremely viscous tarry residue remaining in the still pot was given a very crude distillation, the distillate boiling at B2°C to 1 32°C/2 mm. In an attempt to purify this distillate by a more careful distillation, 5.3 g of a liquid distilling from 53°C to 150°C/5 mm was collected. At this point, much solid sublimate was noted not only in this distillate but in the condenser of the still. 7 g of the solid sublimate was scraped out of the condenser of the still. Recrystallization of the sublimate from ethyl acetate containing a small amount of petroleum ether gave beautiful crystals melting at 175°C to 177°C (5 g). Infrared analysis confirmed that this compound was hydroquinone (9% conversion). 

Fuel soot is an important indicator for oil used in diesel engines and is always present to some extent. A test to measure fuel soot in diesel engine oil is important since it indicates the fuel burning efficiency of the engine. Most tests for fuel soot are conducted by infrared analysis. 

Oxidation of lubricating oil can result in lacquer deposits, metal corrosion, or thickening of the oil. Most lubricants contain oxidation inhibitors. However when additives are used up, oxidation of the oil itself begins. The quantity of oxidation in an oil sample is measured by differential infrared analysis. 

Nitration results from fuel combustion in engines. The products formed are highly acidic and they may leave deposits in combustion areas. Nitration will accelerate oil oxidation. Infrared analysis is used to detect and measure nitration products. 

McClure, G.L., Ed. Computerized Quantitative Infrared Analysis, ASTM STP 934, American Society for Testing and Materials, Philadelphia, 1987. 

Haaland, D.M., et.al. "Application of New Least-squares Methods for the Quantitative Infrared Analysis of Multicomponent Samples", Appl. Spec. 1982 (36) 665-673. 

McClure, G.L., et. al. "Application of Computerized Quantitative Infrared Spectroscopy to the Determination of the Principal Lipids Found in Blood Serum", Computerized Quantitative Infrared Analysis, ASTM STP 934, G.L. McClure, Ed. American Society for Testing and Materials, Philadelphia, 1987, 131-154. 

Steric factors may also be important in situations where alternative modes of reaction are available. Dall Asta (44) examined the ring-opening polymerization of 3-methyl-m-cyclooctene. By infrared analysis of the product formed, he obtained quantitative information about the occurrence of head-to-head and head-to-tail successions. More than 90% of the links in the polymethyloctenamer were of the head-to-tail type, but the sterically more hindered and, therefore, unfavored head-to-head links were also observed (about 5%). Ofstead (39) investigated the ring-opening polymerization of some 1,5-cyclooctadienes substituted at one of the two... 

Fig. 31.—A plot of the log of the trans/cis ratio for polybutadiene against the reciprocal of the absolute temperature of polymerization by a free radical mechanism. (Results of Richardson and Sacher obtained by infrared analysis.)...

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