3.6-3-Membered rings Flashcards
what effect do cyclic molecules have on strain
ring may have additional strain
what doe being in a ring do to flexability
it limits the flexability by tethering the two ends together so they cant rotate independently
why do 3 membered rings have angle strain
sp3 hybridization wants groups to be 109 apart but triangles are 60 degrees apart. a 3 membered ring must be a plainer triangle
why do 3 remembered rings have a lot of torsional strain
when rings are plainer (flat) groups must eclipse each other. but a triangle must be planer
why do 4 membered rings have a lot of angle strain
atoms with sp3 want groups to be 109 degrees apart.
the interal angle of a square is 90 degrees
why do 4 member rings only have moderate torsional strain
because they dont have to be a plainer. this gives them some wiggle room allowing cylobutane to relieve some strain
what is ring inversion
when the two conformers can introvert
what is the energy requirement for 4 membered rings to ring inversion
the energy requirement is very small. 4 membered undergo ring inversion rapidly at room temp
how do are 5 membered rings on angle strain
sp3 wants to be 109 degrees apart. the internal angle of a pentagon are 108. so 5 membered rings have very little angle strain
what is the conformation of 5 membered rings called
envelope
what is the torsional strain of a 5 membered ring
they dont need t be plainar. so they have very little torsional strain
what is the most common ring in nature and synthetic molecules
6 remembered rings
what are some examples of things in nature and synthetic molecules that are made of 6 membered rings
DNA
hormones
sugars
drugs
how are 6 membered rings on angle strain
sp3 wants to be 109 degrees apart hexagons are 120 degrees apart.
6 membered rings have NO angle strain
what is the name for the conformation of a 6 membered ring
chair conformation
how are 6 membered rings on torsional strain
6 membered rings dont have to be planar
why do 6 membered rings have no torsional strain
because every C-C bond is staggered
what makes the inversion of 6 membered rings complex
it does not pass through the plainer conformation (because its so uncomfortable)
1) what are all the different inversion names of 6 membered rings
2)what oder do they rotate through
3) what are there energies like
-chair, 1
-half chair, 4
-twisted boat, 2
-boat, 3
-twisted boat, 2
half chair, 4
chair, 1
what are the two ways to describe chair orientation groups in there conformations
-the 6 groups pointing directly up/down are called axial groups
-the six groups pointing outwards are called equatorial groups
when ring inversion occurs…
axial groups become equatorial groups, the equatorial groups become axial groups
what causes axial groups to become equatorial groups and vise versa
it is the results from rotation of the C-C sigma bonds
what kind of strain could chair conformation possibly have
there is the possibility of steric strain because anything bigger than H can interact with the other axial substituents
what are 1,3-diaxial interations on chair conformation
when any axial substituents larger than H can interact with other axial substituents on chair conformation
