Synthesis of saturated rings via cyclisation

what rings does irreversible cyclisation make?

small and normal rings from molecules that contain both electrophile and nucleophile

on rings, what is a requirement of sn2 reactions to make futher ring

antiperiplanar sigma star orbitals

what is the order of rate dependant on ring size

5 > 6 > 3 > 7 » 4 >8-10 (slowest)

how is entropic cost affected by increase in ring size?

increases with ring size increase because more order must be imposed for ends of the chain to become arranged correctly

how is enthalpic cost affected by increase in ring size?

cost decreases while ring size increases because normal rings are less strained than small rings

what is the thorpe-ingold effect

the presance of bulky geminal substituents in the chain can increase the rate of cyclisation by reducing the entropic cost in the transition state

what rings does irreversible cyclisation make?

normal rings from molecules that contain both electrophile and nucleophile

why is reversible cyclisation not used to make small rings?

1. high ring strain increases potential energy of product making ring formation unfavourable under equilibrium conditions

2. thermodynamic instability, small rings are highly strained as the open-chain is often more stable

3. small rings will readily open in equilibrium therefore need to be formed under irreversible cyclisation