Ch2

Question 1

Alkanes and cycloalkanes are

Answer 1

Saturated Hydrocarbons that only have single bonds

Question 2

Alkanes and cycloalkanes are ___ - hybridized with what degree?

Answer 2

Sp^3 and 109.5

Question 3

What is the first step in naming alkanes?

Answer 3

Finding the longest parent chain

Question 4

When naming alkanes, what does the prefix indicate and what are the first 10?

Answer 4

# of carbons
Meth-1
Eth-2
Prop-3
But-4
Pent-5
Hex-6
Hept-7
Oct-8
Non-9
Dec-10

Question 5

Where are substituents located?

Answer 5

They branch from the parent chain

Question 6

When numbering alkanes, where should you start?

Answer 6

At the end closest to a substituent to give it the lowest possible number

Question 7

If there are mutltiple substituents what should you do?

Answer 7

Number the parent to give lowest numer to substituent closest to an end then list substituents in alphabetical order

Question 8

If there are identical subsitituents

Answer 8

The prefix di, tri, and tetra are not considered in alphabetizing

Question 9

Memorize isopropyl, isobutyl, sec-butyl, tert-butyl, amd neopentyl

Answer 9

**when alphabetizing, ignore hyphenated prefixes sec- and ter-

Question 10

Assume C is binded to _ unless anither substituent is labeled

Answer 10

H

Question 11

1 C is bonded to how many C’s an H’s?
2 C?
3 C?
4 C?

Answer 11

1 carbon and 3 primary H’s
2 Cs and 2 secondary Hs
3 Cs and 1 tertiary H
4 Cs and no Hs

Question 12

How does the nomenclature for cycloalkane work?

Answer 12

Put cyclo before alkane root

If 2 substituents, #1 goes to group that comes first alphabetically

Question 13

What are bicycloalkanes?

Answer 13

Alkanes with two rings that have carbons in common

Question 14

What are bridgehead carbons

Answer 14

The carbon atoms shared by all two-ring sets

Question 15

In bicycloalkanes, the # of carbons in the parent are the two bridgehead carbons plus

Answer 15

All of the bridging carbons

Question 16

Bridge lengths go in ____ in ____ order

Answer 16

Brackets []

Descending

Question 17

Given a choice, give lower numbers to___ or ____

Answer 17

Functional groups or substituents

Question 18

General IUPAC rules

Answer 18

Parent: prefix-infix-suffix
Prefix: # of C atoms
Infix: type of C-C [an: C-C bonds; en: ≥1 C=C bond; yn: ≥1 C triple bond C
Suffix: functional group

Question 19

Suffix functional groups

Answer 19

• e: hydrocarbon (R-H)
• ol: alcohol (R-OH)
• al: aldehyde (R-CH=O)
• amine: amine (RR’R”N)
• one: ketone (R-C(=O)-R’)
• oic acid: carboxylic acid (R-C(=O)-OH)

Question 20

Eclipsed ethane is _ energy / _ stable than staggered ethane because of

Answer 20

Higher
Less
Torsional strain

Question 21

Torisonsl strain is also known as and is?

Answer 21

Bonded strain

The energetic cost of the repulsion of the electrons in eclipsed bonds

Question 22

In butane, the methyl groups move _ each other as you rotate 60°

Answer 22

Away

Question 23

If not anti, it must be

Answer 23

Gauche

Question 24

Non-bonded strain=

Answer 24

Steric strain

Question 25

What is strain?

Answer 25

The increase in the pe of a molecule due to the deviation in its structure from ideal values

Question 26

Components of strain in molecules

Answer 26

``` Angle strain Torsional strain Non-bonded strain Bond strain Coulumbic strain ```

Question 27

Angle strain

Answer 27

Compression or expansion of a bond angle

Question 28

Torsional strain

Answer 28

When bonds are not staggered

Question 29

Non-bonded strain

Answer 29

When two remote groups approach too closely (usually destabilizing, sometimes stabilized); ex:gauche

Question 30

Bond strain

Answer 30

Compression or stretching of bonds

Question 31

Coulumbic strain

Answer 31

Stabilizing or destabilizing

Question 32

Cyclopropane has 28 kcal/mol of strain due to

Answer 32

Angle strain: the C-C-C bond angles are compressed from 109.5° to 60° Torsional strain: there are 6 sets of eclipsed hydrogen interactions with H-C-C-H = 0°

Question 33

Cyclobutane has _ kcal/mol of strain | Cyclopentane has _ kcal/mol of strain

Answer 33

26 | 6.5

Question 34

Planar cyclobutane and cyclopentane try to reduce _ strain but this increases _ strain (a trade-off)

Answer 34

Torsional | Angle

Question 35

In cyclobutane, the best compromise has C-C-C = ___ and H-C-C-H = ___

Answer 35

88° | 24°

Question 36

The two chair conformations in cyclohexane

Answer 36

Have no angle or torsional strain - C-C-C Angles are ideal: 109.5° - all bonds are staggered

Question 37

Boat conformation for cyclohexane

Answer 37

6.5 kcal/mol strain vs. chair conformer Nonbonded strain due to flagpole interactions Eclipsed across two C-C bonds

Question 38

Twist-boat conformation for cyclohexane

Answer 38

5.5 kcal/mol strain vs. chair conformation Nonbonded strain is greatly reduced vs. boat Some torsion strain from partially eclipsed C-H bonds

Question 39

How many gauche interactions does the axial methyl group have in Methylcyclohexane? What about the equatorial conformation?

Answer 39

Axial methyl has gauche interactions and equatorial conformation has no gauche interactions

Question 40

Cis-isomers: | Trans-isomers:

Answer 40

Cis- both groups are on same side of ring | Trans- groups are on opposite sides of the ring

Question 41

Cis- trans isomers are ___ isomers; possible in ___ and ___; and have the same ___ and ___ but are ___

Answer 41

Geometrical Rings and alkenes Molecular formula and atom connectivity Not interconverted via rotation about single bonds

Question 42

Bp of methane, butane, pentane, decane?

Answer 42

Methane = - 164°c Butane = 0°c Pentane = 36°c Decane =174°c

Question 43

``` Intermolecular attractive forces…. Ion/ion = Dipole/dipole= H-bonds = Ion/dipole = ```

Answer 43

Very strong Very weak Moderate Strong

Question 44

London dispersion forces are ____ that depend on

Answer 44

Instantaneous dipole/induced dipole | The total contact surface area between molecules

Question 45

Two limiting cases when comparing two molecules (London dispersion forces)

Answer 45

If the shapes are the same, then the forces increase as the number of atoms increases If the number of carbons is the same, then the forces decrease with increased branching

Question 46

Chrial centers have to have __ different substituents

Answer 46

4

Question 47

Objects that are not superimposable on their mirror images are __ and show handedness… they are different.

Answer 47

Chiral

Question 48

Objects that are superimposable on their mirror images are ___ and do not show handedness. An ___ object has at least one element of symmetry. They are the same

Answer 48

Achiral

Question 49

Plane of symmetry (mirror plane) is an

Answer 49

Imaginary plane through an object where one half is the mirror image of the other half

Question 50

Center of symmetry at the atom (x,y,z) is

Answer 50

The exact same as the atom at (-x,-y,-z) for all atoms in the molecule (inversion center)

Question 51

A tetrahedral atom bonded to four different groups is

Answer 51

A chiral (asymmetric) center

Question 52

A stereocenter is an atom where

Answer 52

The interchange of two groups gives a atereoisomer of the original molecule

Question 53

A carbon bonded to H, CH3, I and Cl is

Answer 53

A chiral center amd stereocenter

Question 54

All chiral centers are

Answer 54

Stereocenters but all stereocenters are not chiral

Question 55

When it comes to R and S, the higher the atomic number, the ….. and if it cannot be assigned using the atoms bonded to the chiral center, use

Answer 55

Higher the priority… the next set of atoms

Question 56

When naming enantiomers…

Answer 56

1. ) locate the chiral center 2. ) prioritize each substituent from 1-4 3. ) draw an arc from 1-3 4. ) CW= R, CCW= S 5. ) but if lowest priority isn’t on dash, switch R or S

Question 57

How do you figure out how many stereoisomers a molecule has?

Answer 57

2^(# of chiral centers)

Question 58

With meso compounds, the mirror place is ____; therefore

Answer 58

The exact same; not an enantiomer

Question 59

What are Meso compounds and what must they have?

Answer 59

An achiral compound possessing two or more chiral centers that must have an internal mirror plane of symmetry or an inversion center

Question 60

Enantiomers have ___ physical and chemical properties while diastereomers have ____ physical and chemical properties

Answer 60

Identical | Different

Question 61

Enantioners become ___ in a chiral environment

Answer 61

Diastereomeric

Question 62

In Fischer projections, vertical bonds ____ while horizontal bonds ____

Answer 62

Vertical: bonds projecting away from you Horizontal: bonds projecting toward you

Question 63

There is angle strain whenever

Answer 63

An angle is less than 109.5 degrees

Question 64

Gauche interactions occur

Answer 64

Whenever 2 non-hydrogen molecules are 60 degrees away from each other