Hot Chromic Acid

Immerse for 10 min at 71—88°C in the solution comprised 1 part chromic oxide (CrOs) and 4 parts distilled water 

The methods in Sections 6.9.1 and 6.9.2 can be run consecutively with an aqueous wash in between to give improved bond strengths. 

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Direct oxidation of ethylpyrazines to the corresponding acetylpyrazines may also be carried out in favourable circumstances using hot chromic acid (75JOC1178). Treatment of 2-ethyl-3-alkylpyrazines with chromic acid yields the corresponding 2-acetyl-3-alkyl-pyrazines in yields of 50-70%. In the absence of the 3-alkyl substituent the yields fall dramatically to less than 10%. Acetylpyrazines are more generally prepared by the inverse addition of a Grignard reagent to a cyanopyrazine. 

Unknown compound D, which has the formula CjqHjq, readily decolorizes a bromine in Ccirbon tetrachloride solution. When D is allowed to react with hydrogen and a catalyst, E is obtained. The M for E has an m/e value of 134. When E is heated with a mixture of nitric and sulfuric acid, only one product is produced. That compound has an M of 179. Heating either D or in hot chromic acid produces a solid F, CgHgO, whose melting point is in excess of 300 degrees Celsius. Give structures for D, E, and F. 

This flask must be cleaned with hot chromic acid solution and then, along with all other glassware used in this preparation, soaked in a base solution, rinsed with distilled waiter, and oven dried. Thermal rearrangement of the intermediate viny 1 ether in a new (untreated) flask resulted in elimination. 

Thomer and Zinche1714 1710 utilized hot chromic acid to carry out oxidative de v ge of tetraphenylethylene oxide and related subetanees (Eq. 426). In a similar manner R be and Hallensieben1484 oxidized atilbcne oxide to benzoic add with chromic add (Eq. 429). 

Chlorinated Polyether. This thermoplastic resists most solvents and is attacked only by nitric acid and fuming sulfuric acids. Thus, it is not capable of being solvent-cemented. Chlorinated polyether parts can be bonded with epoxy, polyurethane, and polysulfide-epoxy adhesives after treatment with a hot chromic acid solution. Tensile shear strength of 1270 psi has been achieved with an epoxy-polysulfide adhesive. 

Side chains of alkylbenzenes are oxidized to benzoic acid derivatives by treatment with hot potassium permanganate or hot chromic acid. Because this oxidation requires severe conditions, it is useful only for making benzoic acid derivatives with no oxidizable functional groups. Oxidation-resistant functional groups such as —Cl, —NO2, —SO3H, and —COOH may be present (Section 17-15A). 

Derivation (1) Nitration of benzoic acid (2) oxidation of o-mtrotolucnc with Mn02 and sulfuric acid, (3) oxidation of p-nitrotoluene by hot chromic acid mixture. 

All glassware was cleaned in hot chromic acid, rinsed with hydrochloric acid, and again rinsed with conductivity water. 

Before performing measurements, the glass cuvette was cleaned with hot chromic acid, rinsed thoroughly with water, and dried in the oven at 110°C. Distilled mercury with a surface tension around 450 mJ/m was used in all experiments. The contact angle formed by a drop of mercury on the wall of the glass cuvette was 115°, as determined with a goniometer. The cavity diameter was measured with a micrometer mounted on the eyepiece of a microscope. The contact forces were measured as described earlier [16,19]. The methodology of such measurements will be discussed in detail in Chapter 2. 

Disulfides Chromic acid, followed by HCI Hot chromic acid, 7-10% HCI, 5%... 

Pretreatment of platinum in hot chromic acid was shown [83] to be equivalent to anodic activation. The electrode has a large reactivity after reduction of the oxygen layer that was formed at open circuit. In contrast to the pretreatment with hot chromic acid, the i — U curve of the first sweep after treatment of the platinum electrode in hot nitric acid does not have the shape characteristic for a clean surface. An intermediate product in the reduction of nitric acid seems to be strongly adsorbed on platinum. It takes several hours of continuous cycling between 0.05 V and 1.4 V at 30mV/sec before the i- U curve regains the regular shape. 

The adhesion of paint inproves as the EPDM content increases. Pretreatment processes include flaming, corona discharge, hot chromic acid, sanding and proprietary primers. 

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