Inspired by an answer to a previous question.
It's hypothesized that extraterrestrial life could be based on silicon rather than carbon as its main structural element.
Are there similar theories about an alternative "life solvent" rather than water?
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3$\begingroup$ Ha, I was just about to ask the very same thing having read the same question! $\endgroup$– rg255Jun 26, 2013 at 20:57
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$\begingroup$ Some scientists are indeed working toward inorganic life see here, bottom part. Not that they succeeded yet, but it's an active research field. $\endgroup$– Gianpaolo RJun 27, 2013 at 6:52
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2 Answers
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This is not a definitive answer.
The solvent closest to water in its properties such as dielectric constant, melting/boiling points, etc are formamide and sulphuric acid.
F S W
Melting point (⁰C) 2 10 0
Boiling point (⁰C) 210 337 100
Dielectric Const 109 84–100 80
Specific gravity 1.133 1.94 1
But water is the simplest i.e made up of only two types of atoms (Which are decently abundant).
Regarding silicon: even though silicon can undergo some level of catenation (silanes) it is not comparable to carbon. Silicon can form polymers like silicone (poly-siloxanes). But I think carbon seems to be more versatile. It is also more abundant (check this out. A nice representation of abundance of different elements in the universe)
Also check this out: it is about exoplanet habitability.
Since certain elements are more abundant than others, the likelihood of them giving rise to life is higher. Therefore water seemingly emerges as the life solvent.
[still most times we see everything in an earth point of view]
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This may not completely answer your question, but provide some information.
Looking at this Wikipedia outline Non water solvents, other possible candidates are ammonia, hydrocarbons even hydrogen fluoride.
Digging a little deeper, this abstract of the article: "Many chemistries could be used to build living systems." (Abstract only) describes the possibilities of ammonia and liquid nitrogen as being potential suitable solvents. Page 678 onwards of the article: "Is there a common chemical model for life in the universe?" also describes other solvents such as ammonia (I should say that there quite a lot of Star Trek references in that paper).
I hope this goes part of the way to help.