Okay, let's tackle at least one problem here. Consider the rotation of 1,2-dichloroethane (BP86/cc-pVDZ): ![rotation of dichloroethane][1] These conformational changes can be further rationalised: - **C** and **C'** are the same conformation, since these are mirror images. - The same applies to **B** and **B'**. - **A** and **C** are local minima and can be referred to as *conformes* in the above given way - **B** and **D** are transition states - they are not stable. If you consider the rotation **A** to **C** as a reaction, this state would mark the maximum energy needed for the conversion. I believe with *reactions* it is meant, that an accurate description of the transition state by InChI is not possible. ---------- For the term non-local chirality I suggest you look at [BINAP][2] or [BINOL][3]. ![structure of BINAP][4] In this case I have used a slightly abridged version of BINAP for educational purposes, where $\ce{Ph -> Me}$. ![R-BINAP][5] ![S-BINAP][6] Other wonderful examples of non-local chirality include [helicenes][7], which have helical chirality. Here is one example of a fancy [azonia derivative of hexahelicene][8] ([parent compound and links][9]). The structure is available at the [Cambridge Crystallographic Data Centre (CCDC) Database][10]. I removed the anion and converted it to xyz coordinates which I include in the appendix. Here are the structures, left *P*-chirality, right *M*-chirality: ![scheme of 8a-azonia[6]helicene][11] ![P-8a-azonia[6]helicene][12]![M-8a-azonia[6]helicene][13] On another account of non/local chirality, there is the planar chirality, as can be seen in *trans*-[Cyclooctene][14] (the bottom two). For further reading I suggest [Neuenschwander *et.al.* "The Conformations of Cyclooctene: Consequences for Epoxidation Chemistry."][15] ![Structures of cyclooctene][16] ---------- [Markush Structures][17] are a kind of summary structure for certain compound classes. A very simple example would be a monosubstituted biphenyl system, where the upper structure is a representation of all three below. However, it is noteworthy, that each instance of a Markush structure can be well explained by InChI. ![biphenyl markush structure][18] More complicated structures are often used in patents and in other scientific publications, usually specifically referring to a very general procedure or mechanism. I found one on wikipedia commons, that could well represent a million molecules: ![markush structure][19] ---------- And another way to break the InChI are [clusters][20]. Although the definition is not very specific, the $\ce{[KO{}^{\mathit{t}}Bu]_4}$ tetramer ([wikipedia][21], [chemspider][22]) certainly contains one. While the monomer can be described via InChI, the tetra- or Polymer should fail. It was published by [Chisholm *et.al.* in Polyhedron][23] and the `*.cif` file can be obtained from CCDB. I cleaned it up a little bit and included the `*.xyz` in the appendix. You can quite nicely see the $\ce{K4}$ tetrahedral cluster in the middle (hydrogens omitted for clarity). ![molecular structure of the potassium butoxide tetramer][24] ---------- Last but not least, I'd like to cover the matter of complicated organometallic molecules. As such I'd like to introduce the [Grubbs' catalysts][25]. [Grubbs][26] obtained the [Nobel Prize in Chemistry 2005][27] for his research in conjunction with Yves Chauvin and Richard R. Schrock. One of the key publications was ["Ring-opening metathesis polymerization (ROMP) of norbornene by a Group VIII carbene complex in protic media"][28]. The crystal structure can also be obtained at CCDC. Another example stems from "[Synthesis and Applications of $\ce{RuCl2(=CHR')(PR3)2}$: The Influence of the Alkylidene Moiety on Metathesis Activity][29]" and is also available via CCDC. This structure can also be found in the appendix. It is generally known as a 1st generation Grubbs catalyst (Hydrogens omitted for clarity). ![scheme of Grubbs I][30]![molecular structure of Grubbs I][31] ---------- #Appendix The following section contains the nuclear coordinates in `*.xyz`(XMol) file format and angstroms as unit. (If not denoted otherwise, structures are obtained at BP86/cc-pVDZ.) 1,2-dichloroethane **A** C 0.000000000 0.000000000 0.000000000 C 0.000000000 0.000000000 1.521307000 Cl 1.723641000 0.000000000 -0.593797000 H -0.486731000 -0.904743000 -0.410753000 H -0.486731000 0.904743000 -0.410753000 Cl -1.723641000 0.000000000 2.115104000 H 0.486731000 -0.904743000 1.932060000 H 0.486731000 0.904743000 1.932060000 1,2-dichloroethane **B** C 0.030242000 0.085780000 -0.007620000 C -0.030242000 0.085780000 1.528927000 Cl 1.518312000 -0.758527000 -0.631286000 H -0.837191000 -0.442465000 -0.444148000 H 0.070555000 1.115212000 -0.412109000 Cl -1.518312000 -0.758527000 2.152593000 H 0.837191000 -0.442465000 1.965455000 H -0.070555000 1.115212000 1.933416000 1,2-dichloroethane **C** C 0.066377000 0.127741000 0.004558000 C -0.066377000 0.127741000 1.516749000 Cl 1.083384000 -1.241726000 -0.615213000 H -0.919786000 0.050600000 -0.492443000 H 0.568277000 1.063384000 -0.317636000 Cl -1.083384000 -1.241726000 2.136520000 H 0.919786000 0.050600000 2.013750000 H -0.568277000 1.063384000 1.838943000 1,2-dichloroethane **D** C 0.164887000 0.141535000 -0.000240000 C -0.164887000 0.141535000 1.521547000 Cl 0.337146000 -1.473219000 -0.795160000 H -0.633932000 0.666019000 -0.558099000 H 1.123149000 0.665665000 -0.177529000 Cl -0.337146000 -1.473219000 2.316468000 H 0.633932000 0.666019000 2.079406000 H -1.123149000 0.665665000 1.698836000 ***R*-BINAP** C -0.086423000 -0.055821000 -0.031546000 C -0.090885000 -0.047699000 1.480085000 C 1.148913000 -0.158515000 2.237313000 C 1.064686000 -0.139089000 3.676951000 C -0.131097000 -0.014450000 4.357670000 C -1.357362000 0.116010000 3.652970000 C -1.345263000 0.107319000 2.211098000 P 2.768926000 -0.321256000 1.451350000 H 1.988600000 -0.233144000 4.265654000 H -0.135982000 -0.008251000 5.459401000 C -2.590782000 0.269421000 4.370415000 C -2.623021000 0.305506000 1.559779000 C 0.437392000 1.073619000 -0.788457000 C 0.410661000 0.991852000 -2.228054000 C -0.079670000 -0.105834000 -2.908992000 C -0.579162000 -1.233570000 -2.204534000 C -0.579999000 -1.219208000 -0.762676000 P 1.107602000 2.557133000 -0.001640000 H 0.790955000 1.839345000 -2.816335000 H -0.077540000 -0.112552000 -4.010726000 C -1.063317000 -2.378355000 -2.921905000 C -1.047368000 -2.424579000 -0.111239000 C -3.792005000 0.431032000 3.705083000 H -2.558632000 0.263827000 5.471798000 H -4.735477000 0.552772000 4.258523000 C -3.797353000 0.457087000 2.279022000 H -2.662047000 0.340912000 0.466043000 H -4.750761000 0.602046000 1.748556000 C -1.503463000 -3.517255000 -0.830391000 H -1.036094000 -2.475958000 0.982488000 H -1.854657000 -4.415344000 -0.299810000 C -1.523650000 -3.499569000 -2.256520000 H -1.052652000 -2.347534000 -4.023279000 H -1.890198000 -4.377463000 -2.809877000 C 4.061075000 -0.509159000 2.730645000 C 2.844045000 -1.846744000 0.446017000 C 1.585856000 3.772639000 -1.280334000 C -0.173490000 3.383258000 1.008127000 H 0.254332000 4.289560000 1.485098000 H -1.067700000 3.703930000 0.418133000 H -0.532498000 2.717241000 1.815764000 H 1.997887000 4.670081000 -0.777298000 H 2.377005000 3.362349000 -1.938832000 H 0.749130000 4.118465000 -1.941170000 H 5.044249000 -0.601334000 2.227532000 H 4.100503000 0.383637000 3.385840000 H 3.944572000 -1.404262000 3.395364000 H 3.842692000 -1.931312000 -0.030903000 H 2.674387000 -2.779210000 1.039384000 H 2.087489000 -1.826871000 -0.361580000 ***S*-BINAP** C -1.383946000 -3.448543000 -2.256996000 C -1.065989000 -2.266144000 -2.910129000 C -0.652376000 -1.110469000 -2.179491000 C -0.563545000 -1.177237000 -0.738280000 C -0.899026000 -2.413534000 -0.098700000 C -1.299620000 -3.519323000 -0.838209000 C -0.154302000 -0.008671000 0.004167000 C 0.166467000 1.182512000 -0.673969000 C 0.072046000 1.221328000 -2.098779000 C -0.323252000 0.113168000 -2.831301000 C -0.061735000 -0.093981000 1.507135000 C -1.110430000 0.372113000 2.322674000 C -0.989013000 0.267385000 3.742090000 C 0.132224000 -0.289631000 4.336601000 C 1.210137000 -0.777916000 3.542877000 C 1.113248000 -0.682564000 2.103804000 C 2.206553000 -1.174312000 1.320794000 C 3.329975000 -1.726929000 1.922868000 C 3.419059000 -1.820539000 3.340084000 C 2.377998000 -1.353835000 4.130094000 P -2.590653000 1.186493000 1.502738000 C -3.750658000 -0.293139000 1.402088000 P 0.636241000 2.692004000 0.339668000 C 2.511918000 2.555623000 0.253510000 C -3.385046000 2.079953000 2.947654000 C 0.388676000 4.078351000 -0.898992000 H -1.802841000 0.635802000 4.383638000 H 0.202504000 -0.360978000 5.434128000 H 0.319305000 2.150696000 -2.632672000 H -0.386992000 0.166196000 -3.930250000 H 2.436377000 -1.419019000 5.228476000 H 4.313241000 -2.262708000 3.805535000 H 2.146133000 -1.110484000 0.224695000 H 4.157224000 -2.097887000 1.298347000 H -0.834575000 -2.478936000 0.997042000 H -1.552289000 -4.458551000 -0.322477000 H -1.128190000 -2.199481000 -4.008215000 H -1.700498000 -4.331984000 -2.832408000 H 2.950535000 3.473538000 0.698290000 H 2.842563000 1.687658000 0.858736000 H 2.884117000 2.439555000 -0.786611000 H 0.678948000 5.023670000 -0.395042000 H 0.990357000 3.982867000 -1.828352000 H -0.686746000 4.150262000 -1.160750000 H -4.302108000 2.573768000 2.564446000 H -3.673500000 1.421270000 3.794842000 H -2.700063000 2.872570000 3.312044000 H -4.742112000 0.063129000 1.051704000 H -3.359638000 -1.014277000 0.656570000 H -3.871382000 -0.807607000 2.379049000 ***M*-8a-azonia\[6\]helicene** (from crystal structure) N 3.565811000 0.259443000 13.724558000 C 7.445232000 -1.196589000 12.564039000 C 8.629416000 -1.762757000 12.151335000 C 8.885324000 -1.978555000 10.783139000 C 7.914184000 -1.694865000 9.864763000 C 6.665024000 -1.171130000 10.265448000 C 5.584378000 -1.088690000 9.330104000 C 4.339207000 -0.800151000 9.738213000 C 4.088732000 -0.406137000 11.083608000 C 2.763235000 -0.187914000 11.543327000 C 2.522579000 0.029096000 12.830042000 C 3.246403000 0.443720000 15.064121000 C 4.198045000 0.692252000 15.970654000 C 5.531025000 0.961394000 15.546639000 C 6.527506000 1.327523000 16.488699000 C 7.769629000 1.675468000 16.086777000 C 8.044342000 1.864594000 14.697195000 C 9.259232000 2.459858000 14.281133000 C 9.466841000 2.806590000 12.982045000 C 8.445715000 2.608977000 12.035743000 C 7.265466000 1.985829000 12.396483000 C 7.061105000 1.553020000 13.720492000 C 5.833567000 0.912900000 14.172787000 C 4.884651000 0.303088000 13.284635000 C 5.151668000 -0.288539000 12.002691000 C 6.444932000 -0.841371000 11.632053000 H 7.296301000 -1.066868000 13.466331000 H 9.304643000 -2.036748000 12.840647000 H 9.760406000 -2.388329000 10.496986000 H 8.038683000 -1.964007000 8.943383000 H 5.780686000 -1.333585000 8.395468000 H 3.604979000 -0.909262000 9.084780000 H 2.029733000 -0.315211000 10.922946000 H 1.672696000 0.060618000 13.273677000 H 2.290439000 0.327335000 15.253240000 H 3.954366000 0.824398000 16.914659000 H 6.255785000 1.333585000 17.427224000 H 8.447606000 1.891266000 16.702563000 H 9.925491000 2.630800000 14.988120000 H 10.286033000 3.200604000 12.619714000 H 8.559741000 2.909640000 11.135042000 H 6.570317000 1.891266000 11.711236000 ***M*-8a-azonia\[6\]helicene** (from BP86/STO-3G) N 0.241946000 3.510759000 13.746203000 C -1.207087000 7.492952000 12.512135000 C -1.801472000 8.692275000 12.089683000 C -2.102492000 8.912745000 10.707738000 C -1.853647000 7.899258000 9.772330000 C -1.278056000 6.643678000 10.182732000 C -1.146616000 5.553783000 9.229249000 C -0.770948000 4.283969000 9.646130000 C -0.392477000 4.045979000 11.023979000 C -0.161103000 2.688046000 11.484550000 C 0.042219000 2.428893000 12.821687000 C 0.400500000 3.183323000 15.136378000 C 0.639392000 4.176721000 16.059802000 C 0.949043000 5.527644000 15.625469000 C 1.361398000 6.519481000 16.597330000 C 1.808770000 7.766658000 16.182869000 C 1.981223000 8.066019000 14.770425000 C 2.627560000 9.287588000 14.362758000 C 2.913363000 9.530579000 13.012425000 C 2.578886000 8.546652000 12.028110000 C 1.916409000 7.363991000 12.392255000 C 1.565834000 7.097902000 13.763105000 C 0.907348000 5.851096000 14.211296000 C 0.281492000 4.885356000 13.292158000 C -0.309154000 5.144896000 11.968134000 C -0.894790000 6.445456000 11.575101000 H -1.007504000 7.339193000 13.585554000 H -2.048406000 9.472285000 12.834293000 H -2.558542000 9.868716000 10.388465000 H -2.123797000 8.035037000 8.708340000 H -1.422274000 5.738729000 8.172836000 H -0.763274000 3.430969000 8.943112000 H -0.251900000 1.843110000 10.776492000 H 0.087281000 1.420761000 13.274365000 H 0.295196000 2.107892000 15.372408000 H 0.697253000 3.916258000 17.133249000 H 1.320711000 6.254708000 17.669775000 H 2.110372000 8.530075000 16.926174000 H 2.921715000 10.016221000 15.141242000 H 3.423497000 10.463796000 12.708003000 H 2.853573000 8.716110000 10.969950000 H 1.691114000 6.611596000 11.618453000 **$\ce{KO{}^{\mathit{t}}Bu}$ tetramer** (from crystal structure) K -1.309381000 -1.309381000 -1.309381000 O -1.313567000 1.313567000 -1.313567000 C -2.107232000 2.107232000 -2.107232000 C -3.502008000 2.298114000 -1.478495000 H -3.842748000 1.465100000 -1.465100000 H -4.060420000 2.821364000 -2.059512000 H -3.516240000 2.821364000 -0.619528000 O -1.313567000 -1.313567000 1.313567000 O 1.313567000 -1.313567000 -1.313567000 K -1.309381000 1.309381000 1.309381000 K 1.309381000 1.309381000 -1.309381000 C -1.478495000 3.502008000 -2.298114000 C -2.298114000 1.478495000 -3.502008000 K 1.309381000 -1.309381000 1.309381000 C -2.107232000 -2.107232000 2.107232000 C 2.107232000 -2.107232000 -2.107232000 O 1.313567000 1.313567000 1.313567000 H -1.465100000 3.842748000 -1.465100000 H -2.059512000 4.060420000 -2.821364000 H -0.619528000 3.516240000 -2.821364000 H -1.465100000 1.465100000 -3.842748000 H -2.821364000 2.059512000 -4.060420000 H -2.821364000 0.619528000 -3.516240000 C -1.478495000 -3.502008000 2.298114000 C -3.502008000 -2.298114000 1.478495000 C -2.298114000 -1.478495000 3.502008000 C 3.502008000 -1.478495000 -2.298114000 C 1.478495000 -2.298114000 -3.502008000 C 2.298114000 -3.502008000 -1.478495000 C 2.107232000 2.107232000 2.107232000 H -1.465100000 -3.842748000 1.465100000 H -2.059512000 -4.060420000 2.821364000 H -0.619528000 -3.516240000 2.821364000 H -3.842748000 -1.465100000 1.465100000 H -4.060420000 -2.821364000 2.059512000 H -3.516240000 -2.821364000 0.619528000 H -1.465100000 -1.465100000 3.842748000 H -2.821364000 -2.059512000 4.060420000 H -2.821364000 -0.619528000 3.516240000 H 1.465100000 -1.465100000 -3.842748000 H 3.842748000 -1.465100000 -1.465100000 H 4.060420000 -2.059512000 -2.821364000 H 3.516240000 -0.619528000 -2.821364000 H 2.059512000 -2.821364000 -4.060420000 H 0.619528000 -2.821364000 -3.516240000 H 1.465100000 -3.842748000 -1.465100000 H 2.821364000 -4.060420000 -2.059512000 H 2.821364000 -3.516240000 -0.619528000 C 1.478495000 2.298114000 3.502008000 C 3.502008000 1.478495000 2.298114000 C 2.298114000 3.502008000 1.478495000 H 1.465100000 1.465100000 3.842748000 H 2.059512000 2.821364000 4.060420000 H 0.619528000 2.821364000 3.516240000 H 3.842748000 1.465100000 1.465100000 H 4.060420000 2.059512000 2.821364000 H 3.516240000 0.619528000 2.821364000 H 1.465100000 3.842748000 1.465100000 H 2.821364000 4.060420000 2.059512000 H 2.821364000 3.516240000 0.619528000 **Grubbs I catalyst** Ru 1.923022 1.782458 4.279841 Cl 3.508375 2.054525 6.061616 P 0.620071 3.495015 5.336792 C 2.967497 2.881791 3.239789 Cl 0.101984 1.197998 2.838894 P 2.855052 -0.401312 3.741075 C 2.954465 3.343954 1.839333 Cl 3.310061 4.678711 -2.473972 C 1.880873 3.257547 0.960743 C 1.973325 3.667349 -0.352875 C 3.185197 4.168660 -0.812833 C 4.252303 4.292067 0.012884 C 4.145603 3.890748 1.341393 C -0.637087 4.207002 4.175769 C -1.979932 4.694567 4.692950 C -2.932151 4.983356 3.538285 C -2.339331 5.946324 2.517809 C -0.957803 5.505405 2.056512 C -0.041546 5.252113 3.235271 C 1.483967 4.856669 6.241316 C 0.518279 5.817396 6.934517 C 1.256971 6.738015 7.899778 C 2.346867 7.495106 7.161401 C 3.302557 6.547168 6.465690 C 2.565538 5.630984 5.497585 C -0.333586 2.698072 6.719178 C -1.014762 1.418485 6.241149 C -1.859827 0.796208 7.358000 C -1.043744 0.536540 8.601177 C -0.361483 1.805588 9.075860 C 0.493782 2.427234 7.979254 C 2.628515 -0.975242 1.991593 C 3.236690 -0.059043 0.937820 C 2.687448 -0.416553 -0.435697 C 2.971677 -1.856587 -0.778868 C 2.466883 -2.799363 0.290130 C 2.999176 -2.423218 1.675026 C 4.622054 -0.540862 4.248552 C 5.523290 0.453308 3.517538 C 6.887074 0.518241 4.175936 C 7.549339 -0.842629 4.233326 C 6.649166 -1.859830 4.903939 C 5.271941 -1.927013 4.232992 C 1.995357 -1.737789 4.704830 C 2.010202 -1.452357 6.212537 C 1.292567 -2.535071 7.008639 C -0.120796 -2.764155 6.507353 C -0.110733 -3.109699 5.031603 C 0.567738 -2.010334 4.218268 H 3.716836 3.154747 3.670969 H 1.120535 2.917815 1.276640 H 1.189061 3.632874 -0.962082 H 5.017596 4.645026 -0.262690 H 4.792512 4.003484 1.897392 H -0.815388 3.399122 3.615754 H -1.902150 5.510235 5.223685 H -2.378700 3.974732 5.228704 H -3.726326 5.342882 3.821555 H -3.181986 4.184074 3.125510 H -2.984577 6.066660 1.748479 H -2.250423 6.781889 2.909669 H -1.054116 4.674447 1.537657 H -0.576082 6.145292 1.467384 H 0.723372 4.965838 2.939787 H 0.125317 6.138803 3.761321 H 1.921040 4.375890 6.908583 H 1.676706 6.235725 8.636983 H -0.145301 5.369077 7.433963 H 0.091950 6.422548 6.224250 H 0.676388 7.347621 8.295653 H 2.791319 8.070082 7.723424 H 1.896364 8.099751 6.522077 H 3.914233 7.048872 6.008409 H 3.698100 6.058287 7.055823 H 3.116098 5.021349 5.094850 H 2.158660 6.180195 4.786983 H -1.006024 3.336226 6.935353 H -1.559257 1.598311 5.456258 H -0.325083 0.765200 6.003389 H -2.608220 1.404611 7.524315 H -2.214635 0.029761 7.044111 H -0.418035 -0.117788 8.397718 H -1.627822 0.182306 9.277813 H 0.176244 1.645756 9.829964 H -1.053680 2.460437 9.333028 H 0.877440 3.225032 8.287287 H 1.235327 1.881817 7.763580 H 1.720632 -0.869158 1.853889 H 4.184273 -0.146643 0.965428 H 3.012517 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