A lot of science-fiction writers have spent a lot of time and energy hypothesizing silicon-based life. This isn't completely insane - if you go down a column of the periodic table, stuff tends to be the same. Fluorine, chlorine, bromine, and iodine all share properties, and so do carbon, silicon, germanium, tin, and lead. Some properties.
Silane, SiH4, is the silicon analogue of methane, CH4. Not nearly the same, though - it flames in air and burns to become sand - SiO2, which is just the silicon analogue of CO2, which is a gas!
An element's chemistry is defined by its interactions with other elements. Silicon makes a great bond with oxygen (and a ridonculous one with fluorine) and this defines much of its chemistry.
Life with silicon wouldn't be anything like life with carbon - can you imagine breathing out sand?
"can you imagine breathing out sand?"
And flatulence would be really, really uncomfortable.
Asimov did a great job tackling the potential alternate chemistries of life. He said that switching from carbon-based life to silicon-based life, it would have to occur in a very different temperature range.
He actually looked at three different examples, including carbon-based life itself: one might be found on Earth-like planets, one might be found on much colder planets, like Jupiter, say, and another might be found only on very hot planets, like Venus. Different compounds would serve the purposes of water, breathable gases, etc. I don't remember any of the specific details, though.
The Asimov article's online.
Interesting. In the Scientific American of this month they are also (again) talking about strange new life forms existing of unusual elements like silicium or peculiar amino acids.
Silicone liquids are remarkably intellgent. Introduce them anywhere near an ultra-high vacuum system and all the proximate carbon-based lifeforms will lethally turn on you. Ditto in trace labs.
What kind of conditions do you need to end up with reduced silicon (silane)? I could see a process analogous to methanotrophy being at least hypothetically possible. The resulting sand would either end up accumulating inside the cell or might perhaps be somehow transported out and dumped into the surrounding medium.
Silicon-based life has, beside the flatulence, another major problem. This damn silicon just doesn't want to form double bonds (too diffuse p-orbitals, bad overlap). Just imagine organic chemistry without double bonds. Say bye to aromatic compounds, carbonyls and other nice things.
hydrogen fluoride etches glass [SiO2+6HF<=>H2SiF6+2H2O] which does a nice job making silicon available for reactions that eventually lead to reduced silicon compounds. there's nothing that precludes hybrid systems where molecule backbones are made of alternating silicon and carbon atoms, the bond is strong and fairly stable and there's no reason to think that redox conditions need to be like earth anyways- life did fine without oxygen for millions of years up until the oxygen catastrophe that is [oxygen killed early anaerobic life] if you absolutely need double bonds, make them in clusters of carbon atoms in the backbone of the chain rather than with silicon. sure it isn't purely based on silicon but life isn't purely based on carbon either, it's actually a carbon-nitrogen polymer backbone and in the case of DNA a phosphate deoxyribose diester backbone.
Seems to me that a fluorine or hydrogen-fluoride-containing atmosphere would be a sine qua non for silicon-based life.
In fact, the fluorine-carbon bond might be TOO strong for a biological system - when you look at how fluorine analogs of some important Earthly biochemicals turn out to be highly toxic... (fluoroacetic acid, frex, locks up the citric acid/Krebs cycle irreversibly).
Silicon might be a better partner for fluorine in a biochemical system than carbon.
Silicon-based life has, beside the flatulence, another major problem. This damn silicon just doesn't want to form double bonds
Introduce them anywhere near an ultra-high vacuum system and all the proximate carbon-based lifeforms will lethally turn on you. Ditto in trace labs.
I THINK ONE COULD CONSIDER AMMONIA AS IT IS DE FACTO TETRAHEDRAL AND COULD MAKE MANY SUITABLE COMPOUNDS..THINK OF THE WATER ANALOGY...
Just imagine organic chemistry without double bonds. Say bye to aromatic compounds, carbonyls and other nice things.