Organic Chemistry Test 2

Front 1

most organic compounds contain

Back 1

rings of carbon atoms

Front 2

cycloalkanes (aliphatic cycle)

Back 2

are saturated cyclic hydrocarbons (general formula (CnH2n))

Front 3

cyclopropane

Back 3

3 carbons (triangle)

Front 4

cyclobutane

Back 4

4 carbons (square)

Front 5

cyclopentane

Back 5

5 carbons (pentagon)

Front 6

cyclohexane

Back 6

6 carbons (hexagon)

Front 7

rules for naming cycloalkanes

Back 7

1. find the parent
2. number the substituents

Front 8

find the parent

Back 8

count the number of carbon atoms in the ring and in the substituents

Front 9

number the substituents

Back 9

choose a point of attachment as number 1
-number the substituent on the ring so that the second substituent has as low a number as possible

Front 10

numbering substituents: when two or more different alkyl groups that could potentially receive the same numbers are present,

Back 10

number them by alphabetical priority (1-ethyl-2-methylcycloheptane, not 2-ethyl-1-methylcyclopentane)

Front 11

numbering substituents: if halogens are present,

Back 11

treat them just like alkyl groups

Front 12

cycloalkanes are less ____ than open chain alkanes

Back 12

flexible

Front 13

much less conformational freedom in

Back 13

cycloalkanes

Front 14

cycloalkanes have 2 faces as viewed edge

Back 14

top face, bottom face

Front 15

isomerism is possible in

Back 15

substituted cycloalkanes

Front 16

there are ___ different 1,2-dimethyl-cyclopropane isomers

Back 16

two (cis and trans)

Front 17

cis

Back 17

on the same side

Front 18

trans

Back 18

"across"; opposite sides

Front 19

isomers

Back 19

different compounds that have the same molecular formula (same number and types of atoms)

Front 20

stereoisomerism

Back 20

compounds which have their atoms connected in the same order but differ in 3D orientation

Front 21

constitutional isomers

Back 21

different connections between atoms

Front 22

stereoisomers

Back 22

same connections but different 3D geometry

Front 23

types of strain seen in cycloalkanes

Back 23

angle strain, torsional strain, steric strain

Front 24

angle strain

Back 24

expansion or compression of bond angles away from most stable bond angle

Front 25

torsional strain

Back 25

eclipsing of bonds on neighboring atoms

Front 26

steric strain

Back 26

repulsive interactions between non-bonded atoms in close proximity.

Front 27

Cyclopropane

Back 27

-3-membered ring must have planar structure
-most strained of all rings

Front 28

strains of cyclopropane

Back 28

angle strain (C-C-C bond angles of 60*)
-torsional strain (all C-H bonds are eclipsed)

Front 29

in cyclopropane, the C-C bond is

Back 29

displaced outward from the internuclear axis
-requires that sp3 based bonds are bent (and weakened)

Front 30

cyclobutane

Back 30

-less angle strain than cyclopropane
-but more torsional strain because of its larger number of ring hydrogens

Front 31

cyclobutane is slightly bent out of plane

Back 31

one carbon atom is about 25* above; the bend increases angle strain but decreases torsional strain

Front 32

cyclopentane

Back 32

-planar cyclopentane would have no angle strain but very high torsional strain
-actual conformations of cyclopentane are nonplanar, reducing torsional strain

Front 33

cyclopentane: __ carbons are in a plane

Back 33

4; the fifth carbon is above or below the plane-- looks like an envelope

Front 34

substituted cyclohexanes occur

Back 34

widely in nature

Front 35

the cyclohexane ring is free of

Back 35

angle strain and torsional strain

Front 36

the conformation of cyclohexane has

Back 36

alternating atoms in a common plane and tetrahedral angles between all carbons
-chair conformation

Front 37

the chair conformation of cyclohexane has two kinds of positions for substituents on the ring

Back 37

-axial
-equatorial

Front 38

each carbon atom in cyclohexane has

Back 38

one axial and one equatorial hydrogen

Front 39

each face of the cyclohexane ring has

Back 39

three axial and three equatorial hydrogens in an alternating arrangement

Front 40

chair conformations are relatively interconvert, resulting in

Back 40

the exchange of axial and equatorial positions by a ring-flip

Front 41

cyclohexane ring rapidly flips between chair conformations at

Back 41

room temperature

Front 42

two conformations of monosubstituted cyclohexane aren't

Back 42

equally stable

Front 43

te equatorial conformer of methyl cyclohexane is ___ stable than the axial by ____

Back 43

more; 7.6 kJ/mol

Front 44

difference between axial and equatorial conformers is due to

Back 44

steric strain caused by 1,3 diaxial interactions
-H atoms of the axial methyl group on C1 are too close to the axial hydrogens
-3 C away on C3 and C5, resulting in 7.6 kJ/mol of steric strain

Front 45

a substituent is almost always more stable in

Back 45

an equatorial position

Front 46

the amount of 1,3-diaxial steric strain depends on

Back 46

the nature and size of the substituent

Front 47

the amount of steric strain increases with

Back 47

the increasing bulk of the alkyl groups

Front 48

in disubstituted cyclohexanes the steric effects of

Back 48

both substituents must be taken into account in both conformations

Front 49

Decalin consists of

Back 49

two cyclohexane rings joined to share two carbon atoms (the bridgehead carbons, C1 and C6) and a common bond

Front 50

two isometric forms of decalin

Back 50

transfused or cis fused

Front 51

in cis-decalin hydrogen atoms at the bridgehead carbons are

Back 51

on the same face of the rings

Front 52

in trans-decalin, the bridgehead hydrogens are on

Back 52

opposite faces