3.6-3-Membered rings

Question 1

what effect do cyclic molecules have on strain

Answer 1

ring may have additional strain

Question 2

what doe being in a ring do to flexability

Answer 2

it limits the flexability by tethering the two ends together so they cant rotate independently

Question 3

why do 3 membered rings have angle strain

Answer 3

sp3 hybridization wants groups to be 109 apart but triangles are 60 degrees apart. a 3 membered ring must be a plainer triangle

Question 4

why do 3 remembered rings have a lot of torsional strain

Answer 4

when rings are plainer (flat) groups must eclipse each other. but a triangle must be planer

Question 5

why do 4 membered rings have a lot of angle strain

Answer 5

atoms with sp3 want groups to be 109 degrees apart.
the interal angle of a square is 90 degrees

Question 6

why do 4 member rings only have moderate torsional strain

Answer 6

because they dont have to be a plainer. this gives them some wiggle room allowing cylobutane to relieve some strain

Question 7

what is ring inversion

Answer 7

when the two conformers can introvert

Question 8

what is the energy requirement for 4 membered rings to ring inversion

Answer 8

the energy requirement is very small. 4 membered undergo ring inversion rapidly at room temp

Question 9

how do are 5 membered rings on angle strain

Answer 9

sp3 wants to be 109 degrees apart. the internal angle of a pentagon are 108. so 5 membered rings have very little angle strain

Question 10

what is the conformation of 5 membered rings called

Answer 10

envelope

Question 11

what is the torsional strain of a 5 membered ring

Answer 11

they dont need t be plainar. so they have very little torsional strain

Question 12

what is the most common ring in nature and synthetic molecules

Answer 12

6 remembered rings

Question 13

what are some examples of things in nature and synthetic molecules that are made of 6 membered rings

Answer 13

DNA
hormones
sugars
drugs

Question 14

how are 6 membered rings on angle strain

Answer 14

sp3 wants to be 109 degrees apart hexagons are 120 degrees apart.
6 membered rings have NO angle strain

Question 15

what is the name for the conformation of a 6 membered ring

Answer 15

chair conformation

Question 16

how are 6 membered rings on torsional strain

Answer 16

6 membered rings dont have to be planar

Question 17

why do 6 membered rings have no torsional strain

Answer 17

because every C-C bond is staggered

Question 18

what makes the inversion of 6 membered rings complex

Answer 18

it does not pass through the plainer conformation (because its so uncomfortable)

Question 19

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

Answer 19

-chair, 1
-half chair, 4
-twisted boat, 2
-boat, 3
-twisted boat, 2
half chair, 4
chair, 1

Question 20

what are the two ways to describe chair orientation groups in there conformations

Answer 20

-the 6 groups pointing directly up/down are called axial groups
-the six groups pointing outwards are called equatorial groups

Question 21

when ring inversion occurs…

Answer 21

axial groups become equatorial groups, the equatorial groups become axial groups

Question 22

what causes axial groups to become equatorial groups and vise versa

Answer 22

it is the results from rotation of the C-C sigma bonds

Question 23

what kind of strain could chair conformation possibly have

Answer 23

there is the possibility of steric strain because anything bigger than H can interact with the other axial substituents

Question 24

what are 1,3-diaxial interations on chair conformation

Answer 24

when any axial substituents larger than H can interact with other axial substituents on chair conformation

Question 25

when you have 1,3-diaxial interactions are all chair conformations equal in energy

Answer 25

no, when the substituent is in the equatorial conformation its favored because theres no steric strain

Question 26

how do we call the quantified energy cost of a groups being axial (in 1,3-diaxial interations)

Answer 26

the amount is referred to as A-values

Question 27

what substituents has a bigger/smaller A value

Answer 27

the bigger the substituent, the larger the A-value