Chapter 2 - Alkanes

Question 1

What are alkanes?

Answer 1

molecules with only C and H atoms and all single bonds.

Question 2

What is the formula for all alkanes?

Answer 2

CnH2n+2

Question 3

What are the characteristics of a line drawing?

Answer 3

1. All ends and connections of lines indicate a carbon
2. hydrogen is not explicityl shown on carbons
3. Hydrogen is always shown on non-carbon atoms

Question 4

What are isomers?

Answer 4

molecules with the same molecular formula, but different structure in some way

Question 5

What is a constitutional isomer?

Answer 5

Isomers that differ in the way the atoms are connected

Question 6

What is the formal naming organization?

Answer 6

IUPAC: International Union of Pure and Applied Chemistry

Question 7

What is an alkyl group?

Answer 7

An alkane in which one hydrogen has been removed
- alkyl groups are usually attached to either another carbon chain or other atoms

Question 8

What is rule number one of naming alkanes?

Answer 8

Identify the parent hydrocarbon: the longest continuous carbon chain
(name becomes the root name)

Question 9

What is rule number two of naming alkanes?

Answer 9

Identify the alkyl substituents that are attached to the parent hydrocarbon chain

Question 10

What is specific about rule number two of naming substituents?

Answer 10

name each substituent on the parent chain with a name and number
- number denotes which carbon atom the substituent is bonded to

Question 11

What is rule number three of naming substituents?

Answer 11

Start on the side closest to the first substituent

Question 12

What is rule number four of naming substituents?

Answer 12

Name the molecule starting with the carbon number of the substituent, the substituent name, and then the parent hydrocarbon

ex: 3-methylhexane

Question 13

What if there are two or more identical substituents?

Answer 13

number the parent chain from the end that gives the lower number to the substituent encountered first.

ex: 2,4 dimethylhexane
not = 3,5 dimethylhexane

Question 14

What happens if there are two or more different substituents?

Answer 14

list them in alphabetical order and number the chain from the end that gives the lower number to the substituent encountered first

Question 15

What happens if there are different substituents in equivalent positions on opposite ends of the parent chain?

Answer 15

Give the substituent of lower alphabetical order the lower number

Question 16

What happens if there are 2 or more parent chains of the same length?

Answer 16

Chose the chain with the most substituents
ex: 3-ethyl-2-methylhexane
not = 3-isopropylhexane

Question 17

What happens when you have substituents that also have substituents?

Answer 17

1. Parent hydrocarbon must start with the carbon attached to the main chain
2. Number the substituent starting from the carbon attached to the main chain
3. Place full name of complex substituent within parenthesis
4. Place in order of substituents using the same rule as for simple substituents

Question 18

What is a primary carbon classification?

Answer 18

Carbon attached to one other carbon

Question 19

What is a secondary carbon classification?

Answer 19

Carbon attached to two other carbons

Question 20

What is a teritary carbon classification

Answer 20

Carbon attached to three other carbons

Question 21

What is a quaternary carbon classification?

Answer 21

Carbon attached to four other carbons

Question 22

What is a cycloalkane?

Answer 22

a saturated hydrocarbon that conatins carbon atoms bonded to form a ring

Question 23

What are the rules for naming a cycloalkane?

Answer 23

1. cyclo is used before the parent name to indicate ring structure
2. When determining the parent hydrocarbon consider the ring and any other alkyl chains separately
3. a mono substituted cycloalkane does not require a number for the substituents
   ex: propylcyclohexane

Question 24

What happens if there is more than one substituent on a cycloalkane?

Answer 24

Position numbers must be used
- start numbering at one substituent
- then number towards the next closest substituent

Question 25

What is a conformational isomer?

Answer 25

molecules that are the same constitutional isomer but differ by a bond rotation

Question 26

What is a staggered conformation?

Answer 26

a conformation about a carbon-carbon single bond in which the atoms or groups on one carbon are as far apart as possible from atoms or groups on an adjacent atom

Question 27

Between staggered and an eclipsed conformation which is more stable?

Answer 27

A staggered conformation is more stable because the atoms are farther away from each other

Question 28

What is an eclipsed conformation?

Answer 28

the atoms or groups on one carbon are as close as possible to the atoms or groups on an adjacent atom

Question 29

What is torsional strain?

Answer 29

resistance to bond twisting in a certain type of chemical compound

Question 30

What is an anti conformation?

Answer 30

staggered conformation in which atoms are the maximum distance apart

Question 31

What is gauche conformation?

Answer 31

staggered conformation in which they are closer together

Question 32

What is steric strain?

Answer 32

when nonbonded atoms separated by four or more bonds are forced closer to each other than atomic radii allow

Question 33

What is the stability of cycloalkanes?

Answer 33

small cycloalkanes have a very large ring srain - 5,6,and 7 membered rings are more stable

Question 34

What is the chair conformation?

Answer 34

all c-c-c bond angles are 110.9 degrees

Question 35

What does it mean for an atom to be equatorial?

Answer 35

perpendicular to imaginary axis

Question 36

What does it mean for an atom to be axial?

Answer 36

parallel to imaginary axis

Question 37

Which is better between axial and equatorial?

Answer 37

Substituents on cyclohexane chairs will always be more stable in the equatorial position

Question 38

What is a stereoisomer?

Answer 38

compounds that have: 1. same molecular formula 2. same connectivity of their atoms 3. different orientation of their atoms in space

Question 39

What is a cis substituent?

Answer 39

substituents are on the same side of the ring

Question 40

What is a trans substituent?

Answer 40

substituents are on the opposite side of the ring - trans isomers are typically in different planes

Question 41

How do you determine if the compound is the same compound or constitutional isomers?

Answer 41

Determine the molecular formal first. Identical molecular formuals indicate either identical compounds or constitutional isomers

Question 42

When does torsional strain typically occur?

Answer 42

it is the strain experienced by the bonds when conformations are not staggered