Allene is the shortest of the series of odd-carbon cumulenes. The even-carbon series of cumulenes are much more explored due to their increased synthetic availability relative to the odd-carbon series. They have co-planar end-groups in the ground-state structure, and achieves helical frontier MOs as its symmetry is reduced by torsion of the end-groups. As the end-groups of butatriene ([3]cumulene) are rotated out of plane, its two π-systems mix and even at small dihedral angles the MOs achieve visually clear helical character. Shown in Figure , the first two excited states belong to the B 1 irreducible representations and each have clear HOMO→LUMO and HOMO-1→LUMO character. At 0 o , the HOMO→LUMO transition is electric dipole allowed, while the HOMO-1→LUMO is magnetic dipole allowed. Already at 10 o torsion, the HOMO and HOMO-1 have become very helical, while the LUMO only has weak helical character that becomes visually clear at higher dihedral angles (Figure ). The transition density also achieves helical character. Especially in the case of the HOMO-1 →LUMO transition where the MO have same helicity, it is visually clear that the helicity of the MOs lead to a helical rotation of the charge. Both transitions achieve parallel non-zero ⃗ µ and ⃗ m. The dihedral angle dependence of the rotatory strength (Figure ) reveals that both transitions quickly achieve an enhanced chiroptical response as the MOs become helical. We note that the two electronic transitions cross at 17 o torsion in an avoided crossing, and thus both MO transitions contribute significantly to both electronic transi-