Lecture 4: newman, cyclos etc

Question 1

true or false: 2 groups bonded by a double bond can rotate around the bond and get difference conformations

Answer 1

false, but be single

Question 2

what are conformations

Answer 2

different spacial arrangements of a molucle that are generate by rotation about single bonds

Question 3

true or false, you can rotate around pie bonds

Answer 3

false, only sigma

Question 4

explain the relationship between different conformations and their stability

Answer 4

diff conformations are possible but not all have the same energy (some are more stable than others)

=rotating changes the proximity of electrons to each other therefore affecting bond length and energy

Question 5

explain staggered conformation

Answer 5

where the dihedral angle b/w bonds at each carbon are 180 degrees from each other and groups attached to c are as far away as possible

Question 6

explain eclipsed formation

Answer 6

atoms bonded to carbons at each end of carbon bond are directly opposive to eeach other and dehidral angle is 0

Question 7

what is the dihedral angle of staggered

Answer 7

18-

Question 8

what is the dihderal angle of escliped

Answer 8

0

Question 9

the H-C-C-H bonds are called what

Answer 9

dehidral

Question 10

what is anti conforatkon

Answer 10

staggered with didegrealk angles of 18

Question 11

what is gauche conformation

Answer 11

dihedral angle of 60 betweeen H-H

Question 12

what conformation has lowest energy

Answer 12

staggered (anti)

Question 13

what conformation has highest energy

Answer 13

ecliped (total)

Question 14

explain why staggered anti is the most stable

Answer 14

because there is less steric interactions
we are putting the molecuels are far as possible therefore less e e repulsion/interaction
and hyperconjuation

Question 15

what is hyperconjugation

Answer 15

favourable overal between filled and unfilled sigma orbitals in stagged conformation
=occurs ehn electrons in filld bonding orbitals move partially into unoccupied anto bonding portion

Question 16

hyperconjugation is greatest in what configuration

Answer 16

staggered anti

the 2 orbitals are parallel

Question 17

what is a steroisomer

Answer 17

same molecular formula and connectivity but different arrrangement of atoms in space

Question 18

what is a constitutional isomer

Answer 18

same molecular formula but diff connectivity

Question 19

what is a conformational isomer

Answer 19

related to one another by BOND rotation

Question 20

true or false: cyclopronane doesnt have ring strain

Answer 20

false, it has alot

Question 21

what is angle strain

Answer 21

deviation from ideal bond angled fue to inherent constraints (rings, size)

Question 22

explain why cyclopropany is not stable in ring

Answer 22

because normally carbons of alkanes are sp3 hybridized therefore their bond angles should be around 109 but with cyclopropane, internal angles are 60 ttherefore there is alot of angle strain

=poor overalap in sp3 orbitals
=c-c bonds are weak and not as stable

Question 23

what is the most stable cylco and why

Answer 23

cyclohexeme because internal angles do not differ alot from nomral bond angle

Question 24

what conformation does cyclohexene adopt to minimize ring sdtraign

Answer 24

chair

Question 25

what are the axial protons

Answer 25

protons that point up and doen

Question 26

what are equitorial protons

Answer 26

point away laterall

Question 27

is there less steric interaction in equirotal or axial

Answer 27

equi

Question 28

but the different conformations of cyclohexane in decreasing order of stability

Answer 28

chair, twist boat, boat, half chair

Question 29

what happens to axial and equitoral protons are we change conformations

Answer 29

axial goes to equi and vice versa

Question 30

which is more stable and why: boat or chair

Answer 30

chair (less sterial interactions)

Question 31

chair conformatios with larger subs at the axial opr equitoral are more stable

Answer 31

equi because no 1,3 diaxiual intereactions

Question 32

true or fals: there are less repulsive forced in the axial methyl conformtionl

Answer 32

false, in equi

Question 33

what are egeometric/cis-trans isomers

Answer 33

they have same moculecular formula, same connectivity but different arrangement of their atoms in space due to presence of double bond

Question 34

true or false: geometric (cis trans) insomeers are also consideered stereosiomers

Answer 34

true

Question 35

cis isomers have subsitutents on same or diff side

Answer 35

same

Question 36

trans insomers have substituents or same or diff sides

Answer 36

diff

Question 37

which conformation, cis or trans, alllows for dipole moment

Answer 37

cis

Question 38

all axial subsituents are trans or cis to each other

Answer 38

trans

Question 39

what is another name for index of hydrogen deficiency

Answer 39

degree of unsaturaion

Question 40

what is IDH

Answer 40

diff in # of pairs of hydrogen attoms between compound of interest in compairson to normal alkane with same number of C

Question 41

what is a saturated hydrocarbon

Answer 41

every H is attached to an H (no rings or double bonds)

Question 42

what is an unsaturated hydrocarbon

Answer 42

C os attached to something that is not a H (double bond, rings)

Question 43

what is the general molecular formula for alkana

Answer 43

cn h2n+2 | minus 2 h for every double bond or ring

Question 44

what is the formula for a cyclioc alkene

Answer 44

cnh2n-2

Question 45

what is the formula for alkene or cyclic alkane

Answer 45

cnh2n

Question 46

1 ring is how many degree of unsaturation

Answer 46

1

Question 47

1 double bond is how many degree of unsat

Answer 47

1

Question 48

2 double bonds, is how many degree unsaturation

Answer 48

2

Question 49

1 triple bond is how mnay degree unsaturation

Answer 49

2

Question 50

2 rings is how many degrees of unsaturation

Answer 50

2

Question 51

how to count IHD for halogents

Answer 51

count halogens as tho they are hydrogens

Question 52

how to count IHD for oxygen

Answer 52

ignore the oxygen atoms and calcualte IHD from remainder of the formula

Question 53

how to count IDH for nitrtogen

Answer 53

subtract one hydrogen for each nitrogen atom and ignore the nitron atoms