Caesium hydroxide

Caesium hydroxide Identifiers InChI InChI=1/Cs.H2O/h;1H2/q+1;/p-1 InChIKey HUCVOHYBFXVBRW-REWHXWOFAG Standard InChI InChI=1S/Cs.H2O/h;1H2/q+1;/p-1 Standard InChIKey HUCVOHYBFXVBRW-UHFFFAOYSA-M CAS number [21351-79-1] EC number 244-344-1 UN number 2682 RTECS FK9800000 ChemSpider 56494 Properties Chemical formula CsOH Molar mass 149.91 g/mol Appearance whitish-yellow solid, deliquescent Density 3.675 g/cm3, solid Melting point 273.3 °C Solubility in water 395.5 g/100 ml at 15 °C Solubility in ethanol soluble Thermochemistry Std enthalpy of formation ΔfHo298 −416.2 kJ/mol Standard molar entropy So298 104.2 J K−1 mol−1 Specific heat capacity C 69.9 J K−1 mol−1 Hazards Material safety data sheet (MSDS) ICSC 1592 EU index number not listed GHS pictograms GHS signal word DANGER GHS hazard statements H330, H314, H318, H302 Flash point non-flammable Related compounds Other anions Caesium oxide Other cations Lithium hydroxide Sodium hydroxide Potassium hydroxide Rubidium hydroxide Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Caesium hydroxide monohydrate Identifiers InChI InChI=1/Cs.2H2O/h;2*1H2/q+1;;/p-1 InChIKey ABSOMGPQFXJESQ-REWHXWOFAC Standard InChI InChI=1S/Cs.2H2O/h;2*1H2/q+1;;/p-1 Standard InChIKey ABSOMGPQFXJESQ-UHFFFAOYSA-M CAS number [35103-79-8] EC number 244-344-1 ChemSpider 10620883 Properties Chemical formula CsOH·H2O Molar mass 167.93 g/mol Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Caesium hydroxide (CsOH) is a chemical compound consisting of an atom of caesium and a hydroxide group (also known as hydroxyl). It is a powerful base, much like other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In fact, caesium hydroxide is powerful enough to quickly corrode through glass.

Due to its high reactivity, caesium hydroxide is extremely hygroscopic. Laboratory caesium hydoxide is typically a hydrate.

It is an anisotropic etchant of silicon, exposing octahedral planes. This technique can create pyramids and regularly-shaped etch pits for uses such as MEMS. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide.

However, this compound is not usually used in experiments as the extraction of caesium is very expensive and the fact that it behaves very much like rubidium hydroxide and potassium hydroxide but reacts chemically stronger than they do.

Caesium hydroxide can be obtained by the following chemical reaction:

2Cs + 2H₂O → 2CsOH + H₂

The above reaction occurs explosively with enough force to shatter a Pyrex beaker.

Further reading

• Corey, E. J.; Noe, Mark C. Preparation of O-Allyl-N-(9-anthracenylmethyl)cinchonidinium Bromide as a Phase Transfer Catalyst for the Enantioselective Alkylation of Glycine Benzophenone Imine tert-Butyl Ester: (4S)-2-(Benzhydrylidenamino)pentanedioic Acid, 1-tert-Butyl Ester-5-Methyl Ester. Org. Synth. 2003, 80, 38, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=v80p0038>.

External links

• International Chemical Safety Card 1592
• NIOSH Pocket Guide to Chemical Hazards 0111