What is torquoselectivity?
Q: What is torquoselectivity?
A: Torquoselectivity is a phenomenon in organic chemistry that describes electrocyclic reactions that produce one isomer more than the other. It occurs when groups of atoms hang from a ring of atoms are more likely to have rotated in a particular direction during the reaction, instead of being equally likely to rotate in both possible directions.
Q: How does torquoselectivity differ from diastereoselectivity?
A: Torquoselectivity is different from the normal diastereoselectivity of pericyclic reactions and goes beyond the Woodward–Hoffmann rules. Diastereoselectivity refers to the preference for one stereoisomer over another, while torquoselectivity refers to the preference for inward or outward rotation of substituents in conrotatory or disrotatory electrocyclic reactions.
Q: What does it mean when a chemical reaction has torquoselective properties?
A: When a chemical reaction has torquoseselective properties, it means that only one direction of rotation was allowed (that is, the direction of rotation on the substituents was favored) and thus produces a single product.
Q: Where did this concept originate from?
A: The concept of torqueselecitivty originated with Kendall N. Houk.
Q: In what cases does steric strain drive selectivity?
A: Steric strain drives selectivity in cases where selective electrocyclic reactions break open rings; different directions of rotation produce distinct structural isomers and steric strain can be used as an explanation for why certain products are formed over others.
Q: How can electron donating and withdrawing groups affect selectvity?
A: Studies have shown that electron donating and withdrawing groups can also change selectvity by altering how likely certain products are formed over others due to their influence on reactant molecules' structures and energies.
Q: Are there any other mechanisms besides electrocyclization which involve torqueselctivty?
A: Yes, there are other mechanisms besides electrocyclization which involve torquelecitivity such as chiral Lewis acid catalysts, induction by neighboring stereocenters (in which case the torquelecitivity is a case of diastereolecitivity), and axial-to-tetrahedral chirality transfer (as seen in Nazarov cyclization reactions).
