I am now inverting the previous question by asking what is the largest angle subtended at a chain of three connected 4-coordinate carbon atoms? Let’s see if further interesting chemistry can be unearthed.
Archive for the ‘Interesting chemistry’ Category
More stereoelectronics galore: hexamethylene triperoxide diamine.
Thursday, September 22nd, 2016Compounds with O-O bonds often have weird properties. For example, artemisinin, which has some fascinating stereoelectronics. Here is another such, recently in the news and known as HMTD (hexamethylene triperoxide diamine). The crystal structure was reported some time ago[cite]10.1021/jp0123841[/cite] and the article included an inspection of the computed wavefunction. However this did not look at the potential stereoelectronics in this species, which I now address here.
A periodic table for anomeric centres, this time with quantified interactions.
Monday, August 8th, 2016The previous post contained an exploration of the anomeric effect as it occurs at an atom centre X for which the effect is manifest in crystal structures. Here I quantify the effect, by selecting the test molecule MeO-X-OMe, where X is of two types:
A periodic table for anomeric centres.
Saturday, August 6th, 2016In the last few posts, I have explored the anomeric effect as it occurs at an atom centre X. Here I try to summarise the atoms for which the effect is manifest in crystal structures.
Stereoelectronic effects galore: bis(trifluoromethyl)trioxide.
Thursday, August 4th, 2016Here is a little molecule that can be said to be pretty electron rich. There are lots of lone pairs present, and not a few electron-deficient σ-bonds. I thought it might be fun to look at the stereoelectronic interactions set up in this little system.
Deuteronium deuteroxide. The why of pD 7.435.
Friday, April 22nd, 2016Earlier, I constructed a possible model of hydronium hydroxide, or H3O+.OH– One way of assessing the quality of the model is to calculate the free energy difference between it and two normal water molecules and compare the result to the measured difference. Here I apply a further test of the model using isotopes.
Oxane oxide: a tautomer of hydrogen peroxide.
Friday, April 15th, 2016If H3N+-O– is viable compared with its tautomer H2N-OH when carrying water bridges, then why not try H2O+-O– vs HO-OH?
Azane oxide, a tautomer of hydroxylamine.
Friday, April 15th, 2016In the previous post I described how hydronium hydroxide or H3O+…HO–, an intermolecular tautomer of water, has recently been observed captured inside an organic cage[cite]10.1002/chem.201406383[/cite] and how the free-standing species in water can be captured computationally with the help of solvating water bridges. Here I explore azane oxide or H3N+-O–,‡ a tautomer of the better known hydroxylamine (H2N-OH).
Hydronium hydroxide: the why of pH 7.
Thursday, April 14th, 2016Ammonium hydroxide (NH4+…OH–) can be characterised quantum mechanically when stabilised by water bridges connecting the ion-pairs. It is a small step from there to hydronium hydroxide, or H3O+…OH–. The measured concentrations [H3O+] ≡ [OH–] give rise of course to the well-known pH 7 of pure water, and converting this ionization constant to a free energy indicates that the solvated ion-pair must be some ~19.1 kcal/mol higher in free energy than water itself.♣ So can a quantum calculation reproduce pH7 for water?