Chapter #2

Question 1

isomers

Answer 1

same molecular formula but different structures

Question 2

what is the only thing that structural isomers share?

Answer 2

their molecular formula

Question 3

what is a synonym for structural isomers

Answer 3

constitutional isomers

Question 4

structural isomers

Answer 4

same molecular formula but different structures (connectivity)

Question 5

physical properties

Answer 5

characteristics of processes that dont change the composition of matter
ex: melting point, boling point, solubility, odor, color, density

Question 6

chemical properties

Answer 6

have to do with the reactivity of the molecule with other molecules and result in changes in chemical composition

Question 7

what are the chemical properties of a molecule attributable to?

Answer 7

the functional groups of the molecule

Question 8

what property or properties do structural isomers have in common?

Answer 8

molecular formula and not necessarily anything else

Question 9

stereoisomers share the same _____

Answer 9

atomic connectivity

Question 10

conformational vs. configurational isomers

Answer 10

conformational isomers: differ in rotation around single bonds (can rotate a bond and get the same molecule)
configurational isomers: can be interconverted only by breaking bonds.

Question 11

draw isomer chart

Answer 11

okay!

Question 12

conformational isomers are the same molecule just at _____

Answer 12

different points in their natural rotation around single bonds.

Question 13

atoms are in their lowest energy state when there is ______ steric repulsion

Answer 13

minimal

Question 14

staggered conformation

Answer 14

there is no overlap of atoms along the line of site

Question 15

anti conformation

Answer 15

staggered conformation with the two largest groups are antiperiplanar.

Question 16

gauche conformation

Answer 16

staggered conformation when the two largest groups are 60 degrees away

Question 17

eclipsed conformation

Answer 17

overlaps

Question 18

totally eclipsed conformation

Answer 18

when the two largest groups are overlapped.

Question 19

name the highest and lowest energy states of conformational isomers

Answer 19

highest: totally eclipsed
lowest: anti

Question 20

for conformational isomers, the higher the energy, the ____ time the molecule will spend in that energetically unfavorable state

Answer 20

lower

Question 21

staggered is always ___ energy that eclipsed conformation

Answer 21

less

Question 22

what are the 3 factors that lead to ring strain of cyclic conformations?

Answer 22

angle strain, torsional strain, and nonbonded (steric) strain

Question 23

angle strain

Answer 23

conformational isomers

when bond angles deviate from their ideal values by being stretched or compressed

Question 24

torsional strain

Answer 24

conformational isomers

when cyclic molecules must assume conformations that have eclipsed or gauche interactions

Question 25

nonbonded strain

Answer 25

conformational isomers also known as van der waals repulsion: when nonadjacent atoms or groups compete for the same space flagpole interactions

Question 26

to alleviate strain, cycloalkanes adopt various ______ conformations

Answer 26

nonplanar

Question 27

what is the most stable form of cyclohexane?

Answer 27

chair

Question 28

regular cyclohexane to chair how to draw it

Answer 28

dash: down wedge: up axial or equatorial depending!

Question 29

when does the cyclohexane molecule pass through the half chair conformation?

Answer 29

when it is undergoing a chair flip

Question 30

what happens on a chair flip?

Answer 30

all axial groups become equitorial and all equitorial groups become axial. BUT all dashes remain dashes and all wedges remain wedges (so pointing up remain up and pointing down remain down)

Question 31

the preferred chair conformation is determined by ____

Answer 31

the larger group

Question 32

configurational isomers

Answer 32

can only change from one form to another by breaking and reforming covalent bonds

Question 33

being nonsuperimposable mirror image means ____

Answer 33

chirality

Question 34

a chiral molecule has ____ substituents

Answer 34

4 different

Question 35

enantiomers

Answer 35

two molecules that are nonsuperimposable mirror images of each other

Question 36

diastereomers

Answer 36

chiral and share the same connectivity but are not mirror images of each other differ at some but not all of their chiral centers

Question 37

discuss the chemical and physical properties of enantiomers

Answer 37

have identical physical and chemical properties two exceptions: optical activity (rotate plane-polarized light in opposite directions) and react differently in chiral environments.

Question 38

what makes a compound optically active?

Answer 38

it has the ability to rotate plane polarized light

Question 39

are achiral molecules optically active?

Answer 39

no

Question 40

compare levorotary and dextrorotary

Answer 40

levo: rotates the plane of polarized light to the left (-) dextro: rotates the plane of polarized light to the right (+)

Question 41

levorotary

Answer 41

rotates plane polarized light counterclockwise (-)

Question 42

dextrorotary

Answer 42

rotates plane polarized light clockwise (+)

Question 43

what are the units of concentration and length in the specific rotation equation?

Answer 43

concentration: g/mL length: dm

Question 44

discuss optical activity in a racemic mixture

Answer 44

none

Question 45

racemic mixture

Answer 45

when both enantiomers are present in equal concentrations

Question 46

can you tell d- and l- rotation from structure of the compound?

Answer 46

no, it is determined experimentally.

Question 47

how do you experimentally separate enantiomers?

Answer 47

react them with a different enantiomer and it will produce 2 diastereomers which can be separated and then reacted to produce original enantiomers.

Question 48

diastereomers

Answer 48

a molecule has two or more stereogenic centers and differs at some but not all of these centers

Question 49

diastereomers have ____ chemical properties and ____ physical properties

Answer 49

different (sometimes react similarly because they have similar functional groups) different

Question 50

what is another name for cis/trans isomers?

Answer 50

geometric isomers

Question 51

discuss plane of symmetry within a molecule and optical activity

Answer 51

even if a molecule has chiral centers, if it has a plane of symmetry, it will not be optically active

Question 52

meso compound

Answer 52

a molecule with an internal plane of symmetry and chiral centers

Question 53

Priority via the Cahn-Ingold-Prelog rules

Answer 53

priority is assigned based on the atom bonded to the double bond carbons: the higher the atomic number, the higher the priority comparing atoms attached to the same OG carbon.

Question 54

steps of naming R and S forms

Answer 54

1. number substituents based on priority (atomic number) 2. orient the substituent with lowest priority in the back of the molecule (any time 2 groups are switched on a chiral carbon, the stereochemistry is inverted) 3. draw circle. clockwise: R. counterclockwise: S. 4. name it (S) or (R) in front of the name and numbered if more than one.

Question 55

rotating a fischer projection _____ changes R vs. S

Answer 55

90 degrees | 180 degrees reverts it back to normal

Question 56

discuss physical and chemical properties for structural isomers

Answer 56

different and different

Question 57

what is the formula for maximum stereoisomers of a compound?

Answer 57

2^n where n is the number of chiral centers

Question 58

absolute configuration

Answer 58

R and S

Question 59

relative configuration

Answer 59

the position of atoms or groups in space in relation to (i.e., relative to) something else in the molecule. like cis and trans or looking at whole molecule D vs. L