document: HOMO–LUMO energy band gaps between ylides and their pyrene adducts propose that the 1,3-DC of second pyridinium ylides to ylidepyrene adducts are HOMOylide–LUMOylide–pyrene controlled since the energy band gap is smaller than HOMOylide–pyrene–LUMOylide. Regioselectivity of second cycloaddition was predicted using the atomic orbital coefficients corresponding to HOMOylide–LUMOylide–pyrene. According to Fukui [33], reactions can be favorable in the direction of maximal HOMO–LUMO overlapping of larger coefficients at the reactive sites. The most favorable interactions between corresponding ylides and ylidepyrene adducts to form the most favorable regioisomer conformation are given in Fig. 3. Second ylide addition to ylidepyrene structure is therefore anticipated to proceed via ylideC2/C6–ylidepyrene-C3 and ylideC7–ylidepyrene/C2 interactions to produce the same regioisomer conformations. Considering the theoretical calculations performed for pyrrolidine attached pyrene structure, it is also expected that formation of the same type of regioisomers are favorable for SWNTs after the 1,3-DC of pyridinium ylides, Fig. 3.
doc_bio_tags: B O O O O B O O B I O O O O O B I I O B O O B O O O O O O O O O B B I I I O O O O B I I O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O B O O O O B I I I O O O O O O B O O B O O O O O O O O O O O O O O O B I O O B I O O B I I O O O O O O B I I I I I I O O O B O O O O O B O O
extractive_keyphrases: atomic orbital coefficients formation of the same type of regioisomers homo–lumo homoylide–lumoylide–pyrene homoylide–pyrene–lumoylide most favorable regioisomer conformation pyrene adducts pyrrolidine attached pyrene regioisomer conformations regioselectivity of second cycloaddition second pyridinium ylides swnts theoretical calculations ylide ylidepyrene ylides
abstractive_keyphrases: 1,3-dc 1,3-dc of pyridinium ylides maximal homo–lumo overlapping regioisomers ylidec2/c6–ylidepyrene-c3 ylidec7–ylidepyrene/c2 ylidepyrene adducts ylides and ylidepyrene adducts