Figure 3.3
In this figure we see selected stationary points and molecular orbitals for the controtatory 4-pi-electrocyclic ring closure of (E,E)-hexa-2,4-diene.
The starting point of this reaction is (E,E)-hexa-2,4-diene:
cb_005.mol
and the corresponding Gaussian input file for this compound in its cis-conformation is:
#p b3lyp/6-31G(d,p) int=finegrid freq pop=npa cb_005 b3lyp/6-31G(d,p) opt TS 0 1 C,0,0.0766130374,0.7297164659,0.7646202356 C,0,-0.116808485,1.5478211981,-0.2812899902 C,0,0.116808485,-1.5478211978,-0.2812899917 C,0,-0.0766130374,-0.7297164666,0.7646202349 H,0,0.3562656452,1.1761527996,1.7202213391 H,0,-0.3562656452,-1.1761528012,1.720221338 C,0,0.0824087089,3.0338425878,-0.2573432823 H,0,-0.8383793058,3.5658922008,-0.5296214102 H,0,0.3970851365,3.3823588517,0.7310329642 H,0,0.84554325,3.344855093,-0.9830423662 C,0,-0.0824087089,-3.0338425875,-0.2573432851 H,0,0.8383793058,-3.5658922003,-0.5296214135 H,0,-0.3970851365,-3.3823588523,0.7310329611 H,0,-0.84554325,-3.3448550921,-0.9830423693 H,0,-0.4525255232,1.1205374846,-1.2264120502 H,0,0.4525255232,-1.1205374834,-1.2264120512
The preferred transition state for this electrocyclic ring closure indicates a preference for conrotatory movement of the reaction centers:
cb_006_invts.mol
The corresponding Gaussian input file for the transition state is:
#p b3lyp/6-31G(d,p) int=finegrid freq pop=npa cb_006 b3lyp/6-31G(d,p) opt TS 0 1 C 1.02012000 -0.14166100 -0.35499100 C 0.68235400 1.22141100 -0.07890400 H 1.39178700 2.03385700 0.07685500 C -1.02012000 -0.14166000 0.35499100 C -0.68235400 1.22141100 0.07890400 H -1.39178600 2.03385700 -0.07685500 C 2.27949500 -0.82145000 0.12241700 H 3.11761600 -0.61755900 -0.56110000 H 2.15617300 -1.90932500 0.14893400 H 2.57764700 -0.48887000 1.12124000 C -2.27949500 -0.82144900 -0.12241700 H -2.15615900 -1.90932200 -0.14896900 H -2.57766700 -0.48884300 -1.12122500 H -3.11760700 -0.61759200 0.56112100 H 0.59433100 -0.56791100 -1.25756300 H -0.59433100 -0.56791100 1.25756200
Trans-3,4-dimethylcyclobutene is the reaction product:
cb_003_inv.mol
and the corresponding Gaussian input file for this compound is:
#p b3lyp/6-31G(d,p) int=finegrid freq pop=npa cb_003 b3lyp/6-31G(d,p) opt min 0 1 C -0.57213900 1.32080300 0.34759700 C -0.67245000 -0.19679500 0.41683700 C 0.67245200 -0.19679500 -0.41683900 C 0.57213800 1.32080600 -0.34759500 H -1.21862900 2.10758700 0.72787500 H -0.51799000 -0.59459200 1.42967300 H 1.21862600 2.10759300 -0.72787100 C -1.89176800 -0.86063700 -0.21923700 H -2.80097200 -0.65153500 0.35589300 H -1.77210300 -1.94905000 -0.26535600 H -2.05094000 -0.49264200 -1.23882000 C 1.89176700 -0.86063800 0.21923700 H 2.80097500 -0.65153600 -0.35588600 H 1.77210200 -1.94905100 0.26535300 H 2.05093500 -0.49264500 1.23882200 H 0.51799200 -0.59458700 -1.42967700