Nitrogen dioxide is dimerized to form dinitrogen tetroxide according to the equation $\ce{2NO2 -> N2O4}$. How do two molecules of one compound fuse to form another?
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2$\begingroup$ I think you can answer your question easily. Draw the Lewis structures for NO2 and you'll see how the dimer is obvious solution to some problem. $\endgroup$– ssavecFeb 23, 2016 at 7:55
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$\begingroup$ The same way as any other reaction takes place? $\endgroup$– bonFeb 23, 2016 at 12:38
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2 Answers
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The electronic structure of NO2 leaves an unpaired electron on the nitrogen. This is one of the reasons it is quite reactive. But it is also the reason why it can easily dimerise to N2O4 as the two unpaired electrons in two molecules of the gas can pair up creating a weak bond. The dimer is favoured at low temperatures when the thermal energy isn't large enough to shake the dimer apart (I'm simplifying a bit). This is why the colour of the gas changes depending on temperature as the dimer is colourless but the NO2 is brown.
answered Jul 16, 2016 at 13:20
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$\begingroup$ This is very correct. However, when reading the questions it appears to me the person asking it (on a rather basic level) did not understand what the dimer would look like. There seems to be a misconception about the binding process, given the phrasing of "fusing". The crucial bit here is to understand that the atoms of the 2 nitrogen dioxide molecules are not broken apart and refused to form something new, but that the molecules stay intact and bind together. See also my answer. $\endgroup$– tipaviJul 16, 2016 at 16:11
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Maybe the confusion arises because you're unclear about what a dimer is. The molecules don't "fuse". They form a bond.
It's better to think of the dimer as $(NO_2)_2$ rather than $N_2O_4$.
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$\begingroup$ I think it would be even clearer if you were to include the Lewis structure. $\endgroup$ Feb 17, 2018 at 3:36