The aci form of nitroethane, $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{NO}{}_2$, is

Nitro-aci tautomerism moves an alpha hydrogen from carbon to an oxygen of the nitro group and shifts the double bond onto nitrogen. This converts $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{NO}{}_2$ into $\mathrm{CH}{}_3\mathrm{CH}=\mathrm{N}(\mathrm{O})\mathrm{OH}$. Ethyl nitrite, glycine and methyl carbamate are isomers of $\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{NO}{}_2$ but not tautomers.