A chromate ester is a chemical structure that contains a

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...

atom (

symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...

Cr) in a +6

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

that is connected via an

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

(O) linkage to a

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

(C) atom. The Cr itself is in its chromate form, with several oxygens attached, and the Cr–O–C attachment makes this chemical group structurally similar to other

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

functional groups. They can be synthesized from various chromium(VI) metal compounds, such as CrO₃, chromium chloride complexes, and aqueous chromate ions, and tend to react via

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

reactions to liberate chromium(IV). Chromate esters are the key

reactive intermediate In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these comp ...

s in the

Jones oxidation The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation o ...

, the mechanistically related oxidations using

pyridinium dichromate The pyridinium dichromate (PDC) or Cornforth reagent is a pyridinium salt of dichromate with the chemical formula 5H5NHsub>2 r2O7 This compound is named after the Australian-British chemist Sir John Warcup Cornforth (b. 1917) who introduced it ...

pyridinium chlorochromate Pyridinium chlorochromate (PCC) is a yellow-orange salt (chemistry), salt with the chemical formula, formula 5H5NH rO3Cl��. It is a reagent in organic synthesis used primarily for organic redox reaction, oxidation of Alcohol (chemistry), al ...

. Chromate esters of

allyl alcohol Allyl alcohol ( IUPAC name: prop-2-en-1-ol) is an organic compound with the structural formula . Like many alcohols, it is a water-soluble, colourless liquid. It is more toxic than typical small alcohols. Allyl alcohol is used as a raw material ...

s may isomerize via formal ,3sigmatropic shift to give rearranged enone products. An example of an isolable chromate ester is ((CH₃)₃CO)₂CrO₂.Fillmore Freeman, "Di-tert-butyl Chromate" Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley & Sons, Ltd.

References

{{ester-stub Chromates Esters