Shown in Figure , we assess the HOMO of achiral 1,1-Me- [8]cumulene and chiral S -1,9-Me- [8]cumulene. The former is a clear case of a rectilinear HOMO, and the latter of a helical HOMO. In the graph of the cumulated sum, we see that the rectilinear HOMO of 1,1-Me- [8]cumulene increases with a series of steps. Its cumulated sum of the twist does not change at all for the first ⇠ 2 Å and then makes an abrupt jump of ⇡ rad (180 ) when there is a node in the MO. The HOMO of S -1,9-Me- [8]cumulene has an almost constant increase in the cumulated sum and, as explained in Methods, this is one of the defining features of a cylindrical helix. The MAD for the helical MO is 4, which gives an indication of a "low" value that suggests an almost perfect helix. In comparison, the MAD of the rectilinear HOMO of 1,1-Me- [8]cumulene is 51.