Ammonium cerium(IV) nitrate

Ammonium cerium(IV) nitrate
General
Systematic name	Diammonium cerium(IV) nitrate
Other names	Ceric ammonium nitrate (CAN)
Molecular formula	(NH₄)₂Ce(NO₃)₆
Molar mass	548.26 g/mol
Appearance	orange-red crystalline solid
CAS number	^*
EINECS number	240-827-6
Properties
Solubility in water	141 g/100 ml (25°C) 227 g/100 ml (80°C)
Melting point	107-108 °C (? K)
Structure
Coordination geometry	Icosahedral
Crystal structure	Monoclinic
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other cations	Ammonium cerium(III) nitrate
Related compounds	Ammonium nitrate Cerium(IV) nitrate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox

Ammonium cerium(IV) nitrate, more commonly called ceric ammonium nitrate or in lab jargon "CAN", but also ammonium nitratocerate(IV) and ammonium hexanitratocerate(IV), is an oxidising agent widely used in organic synthesis. This orange-red, water-soluble salt has the formula (NH₄)₂Ce(NO₃)₆. This compound is used as a standard oxidant in quantitative analysis,

Properties and structure

Two components comprise this salt, the anion ^*^2- and a pair of NH₄⁺ counter ions, which are not involved in the reactions of CAN. In the anion each nitrato group is linked to the cerium atom in a bidentate manner as shown below:

Although the N-O bonds (on the metal side of the nitrato group) are unsymmetrical. The anion ^*^2- has idealized T_h symmetry. The CeO₁₂ core defines an icosahedron.

Preparation

The anion ^*^2- is generated by dissolving Ce₂O₃ in hot concentrated HNO₃.

Key reactions

(NH₄)₂Ce(NO₃)₆ is a stronger oxidizing agent (E° ~ 0.96 V vs. N.H.E.) than even Cl₂. Few shelf-stable reagents are stronger oxidants. In the redox process Ce(IV) is converted to Ce(III), a one-electron change, signalled by the fading of the solution color from orange to a pale yellow (providing that the substrate and product is not strongly colored). CAN is useful as an oxidant for many functional groups, some of which are listed below.

Oxidation of C-H bonds:
- Alkenes produces dinitroxylation, although the outcome is solvent-dependent.
- Methylarenes undergo benzylic oxidation.
Oxidation of alcohols, phenols, and ethers
- Benzylic alcohols are converted into carbonyl compounds.
- Quinones are produced from catechols and hydroquinones.
Oxidation of nitroalkanes
- An alternative to the Nef reaction, e.g. for ketomacrolide synthesis where complicating side reactions usually encountered using other reagents are avoided using CAN.

Oxidative halogenation can be promoted by CAN as an in situ oxidant,for benzylic bromination, the iodination of ketones and uracil derivatives.

Applications

It has been shown that catalytic amounts of aqueous CAN in tap water can be used to efficiently synthesize various quinoxaline derivates in excellent yields. Quinoxaline derivates are known for their applications in areas such as the following: dyes, organic semiconductors, and DNA cleaving agents. These derivatives are also important components in antibiotics such as Echinomycin and Actinomycin which are known to inhibit the growth of Gram-positive bacteria and can be used against transportable tumors. There are many methods for the synthesis of quinoxaline derivatives, however, most of these suffer from unsatisfactory product yields, expensive metal precursors, harsh reaction conditions for the use of those precursors, as well as other problems. CAN provides both an inexpensive and nontoxic solution to these problems.

CAN is also an important component of Chrome etchant, a material that is used in the production of LCDs.

References

Budavari, Susan (Ed.). (1989). The Merck Index (11th ed.). Rahway, NJ: Merck.
Macintyre, J. E. (Ed.). (1992). Dictionary of Inorganic Compounds (Vol. 3). London: Chapman & Hall.
More, Shivaji V.; Sastry, N.V.; Yao, Ching-Fa. "Cerium (IV) Ammonium Nitrate (CAN) as a Catalyst in Tap Water: A Simple, Proficient and Green Approach for the Synthesis of Quinoxalines" Green Chemistry (2006) volume 8, pp.91-95.
Wells, A.F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford, UK: Clarendon Press.
Connelly, N. G.; Geiger, W. E. "Chemical Redox Agents for Organometallic Chemistry" Chemical Reviews (1996), vol. 96, pp.877-910

External links

Ammonium compounds | Cerium compounds | Nitrates | Coordination compounds