Ethanol dichromate

Chrome alum is also obtained if the acidified dichromate is boiled with ethanol, the ethanal formed distilling off. 

To prepare acetic acid, aqueous ethanol is added gradually to a hot mixture of aqueous sodium dichromate and sulphuric acid. The oxidising mixture is now always in excess, and therefore the oxidation proceeds as far as possible moreover, the reaction is carried out under reflux, so that any acetaldehyde which volatilises is returned to the oxidising mixture. Hence the final product contains only a small amount of acetaldehyde. 

Required Ethanol, 40 ml. sodium dichromate, 50 g. sulphuric acid, 17 ml. 

Sodium dichromate is used instead of the potassium salt because it is far more soluble in water, and is not precipitated from its aqueous solution by addition of the ethanol. It is also cheaper than the potassium salt, but has the disadvantage of being deliquescent. 

Required Sulphuric acid, 3-3 ml. sodium dichromate, 3-5 g. ethanol, 1-5 ml. copper carbonate, 1 5 g. 

In a similar manner, ethanol can be oxidized by the dichromate ion to form a compound called acetaldehyde, CHaCHO. The molecular structure of acetaldehyde, which is similar to that of formaldehyde, is shown at the bottom in Figure 18-6. We see that the molecule is structurally similar to formaldehyde. The methyl group, —CH3, replaces one of the hydrogens of formaldehyde. The balanced equation for the formation of acetaldehyde from ethanol is... 

After use the cells must be carefully washed with distilled water, or if an organic solvent which is not miscible with water was employed, they must be rinsed with a solvent which is miscible with both the solvent used and with water, and then well washed with distilled water. Finally, they are rinsed with ethanol followed by drying, which may be conveniently done in a vacuum desiccator. Cells which have become contaminated can usually be cleaned by soaking in a solution of a detergent, such as Teepol. For obstinate contamination recourse may be made to the use of sulphuric acid-sodium dichromate cleaning mixture (CAUTION ) (Section 3.8). After soaking overnight the cells are well washed with water and finally dried. 

Hydrazones of the form ArCH=NNH2 react with HgO in solvents such as diglyme or ethanol to give nitriles (ArCN). Aromatic hydroxylamines (Ar—NH-—OH) are easily oxidized to nitroso compounds (Ar—N=0), most commonly by acid dichromate. ... 

Spirothiopyrans 45b including a benzopyrylium ring have been prepared in one step by condensation of 2-aminovinyl-3-formyl chromone-4-thione 47 with 1,2,3,3-tetramethylindolinium salts in ethanol (Scheme 25).90 The precursor 47 is prepared from 3-carboxymethylene-2-methyl-chromone-4-thione 48. First, oxidation of 48 with pyridinium dichromate in CH2C12, and then condensation with dimethyl formamide dimethyl acetal in benzene gave compound 47. 

Ring D inversion seems to be a crucial step in biogenetic transformations of protoberberines to related alkaloids such as rhoeadine, retroprotoberberine, spirobenzylisoquinoline, and indenobenzazepine alkaloids. 8,14-Cyclober-bin-13-ol 478 derived from berberine (15) was successively treated with ethyl chloroformate, silver nitrate, and pyridinium dichromate (PDC) in dimethyl-formamide to give the keto oxazolidinone 479 (Scheme 98). Heating of 479 with 10% aqueous sodium hydroxide in ethanol effected hydrolysis, retro-aldol reaction, cyclization, and dehydration to provide successfully the... 

During preparation of acetic acid by acid dichromate oxidation of ethanol according to a published procedure, minor explosions occurred on two occasions after refluxing had been discontinued. This possibly may have involved formation of acetaldehyde (which has an AIT of 140°C) and ingress of air into the reaction vessel as it cooled [1]. Runaway reactions during small scale oxidation of ethanol have apparently been experienced by many teachers, poor initial mixing or starting too cool may be the cause [2],... 

Kiba et al. [93] has described a method for determining this element in marine sediments. The sample is heated with a mixture of potassium dichromate and condensed phosphoric acid (prepared by dehydrating phosphoric acid at 300 °C). The ruthenium is distilled off as RuC>4, collected in 6 M hydrochloric acid-ethanol and determined spectrophotometrically (with thiourea) or radiometrically. Osmium is separated by prior distillation with a mixture of condensed phosphoric acid and Ce(S04)2. In the separation of ruthenium-osmium mixtures recovery of each element ranged from 96.8 to 105.0%. 

Reich (1) A process for purifying carbon dioxide obtained by fermentation. It is first scrubbed by aqueous ethanol, then by aqueous potassium dichromate to oxidize organic compounds, and finally with concentrated sulfuric acid to dry it. Developed in the 1920s by G. T. Reich. 

Figure 2.1(A) shows raw fruit. The crisp, sharp-tasting fruit hecomes soft and sweet when it is cooked. Figure 2.1(B) shows a chemist accelerating the tranformation of ethanol into ethanoic acid, hy adding potassium dichromate and sulfuric acid.

Source Manufactured by oxidizing ethanol with sodium dichromate and sulfuric acid or from acetylene, dilute sulfuric acid, and mercuric oxide catalyst. 

The equation shows that alcohol in the form of ethanol reacts with an orange solution of potassium dichromate to produce a green solution of chromic sulfate. The source of alcohol is the suspect s breath. More alcohol produces a greater color change. The breath analyzer measures this color change and coverts this measurement into an amount of alcohol in the blood. 

Preparation of Chromium Potassium Alum. Pour 25 ml of water into a 50-ml beaker and dissolve 2.5 g of potassium dichromate in it. Add a concentrated sulphuric acid solution to the mixture (one-and-a-half the stoichiometric amount). First cool the mixture to room temperature, and then put it into water with ice and add ethanol dropwise from a dropping funnel until the solution acquires a violet colour (sulphur dioxide can also be used as the reducing agent). Keep the temperature below 40 °C (why ). After adding the ethanol, let the solution stand to your next lesson. Write the equation of the reaction. 

When suspected drunk drivers are tested with a Breathalyzer, the alcohol (ethanol) in the exhaled breath is oxidized to acetic acid with an acidic solution of potassium dichromate ... 

Ethanol can be oxidised to ethanoic acid (an organic acid also called acetic acid) by powerful oxidising agents, such as warm acidified potassium dichromate(vi), or potassium manganate(vu). 

During the reaction the orange colour of potassium dichromate(vi) changes to a dark green (Figure 15.5) as the ethanol is oxidised to ethanoic acid. 

Figure 15.5 Orange potassium dichromate(vi) slowly turns green as it oxidises ethanol to ethanoic acid. Potassium manganate(vn) turns from purple to colourless.

Add ethanol dropwise to a warm mixture of potassium dichromate(vi) and dilute sulfuric acid. R... 

Dichromate ion is reddish-orange, chromium(III) ion is green. When breath containing ethanol is passed through a solution containing dichromate ion, ethanol is oxidized and dichromate ion is reduced to green chromium(III) ion. 

Ethanol and Sulfuric Acid. Oxidation of ethanol with acid dichromate may result in minor explosion.4... 

---