Chem 219: Module 2 Exam Questions with Verified
Answers Graded A+
What are conformers? - ANSWER -Different shapes of molecules that are derived by
rotations of single bonds.
What does the Newman projection do? - ANSWER -It shows the conformation of
molecules when looking down a particular bond axis.
What is the difference in hydrogen placement between an eclipsed confirmation and a
staggered one? - ANSWER -The hydrogens do not overlap in staggered but they do in
eclipsed.
What are Alkanes? - ANSWER -They are saturated hydrocarbons because their
skeleton is only composed of C-C single bonds.
How can alkanes exist? - ANSWER -They can be linear, branched or exist in ring
formations called cycloalkanes.
Describe a higher/more complex alkane structure: - ANSWER -They will have more
carbons and/or increased structural diversity.
What is the general formula of Alkanes? - ANSWER -CnH2n+2
The names of the alkanes reflect? - ANSWER -The number of carbons present.
How many isomers does each alkane have from 1-10 - ANSWER -
1,1,1,2,3,5,9,18,35,75
Name the first ten prefix of alkanes: - ANSWER -Methane, ethane, propane, butane,
pentane, hexane, heptane, octane, nonane, decane.
As the molecular weight increases: - ANSWER -The number of isomers increase.
What does the suffix -ane mean? - ANSWER -Denotes a saturated hydrocarbon. It is
used for all acyclic saturated alkanes
What is nomenclature? - ANSWER -The naming of a molecular structure. Historically
they were named after their source, now they are systemic.
Why is nomenclature important? - ANSWER -Because we cannot remember all the
prefixes since a MF composed of carbons can have several different patterns of
connectivity.
, What is it meant by the systemic approach? - ANSWER -There are now methods of
naming molecules so that they all have unique names. You can then determine the
structure from only the name and vice-versa.
IUPAC rules for naming branced alkanes: - ANSWER -1. Find the parent name by
identifying the longest continuous chain of carbons.
2. Number the parent chain. (begin at the end of the chain nearest to the first branch.)
3. If there are two equally long continuous chains, select the one with most branches.
4. If the first branch point is the same distance, choose the one that gives the lowest
substituents.
5. If the substituents are both equidistant then choose the numbering so the substituent
goes with the higher alphabetic priority.
How are linear alkanes named? - ANSWER -By combining the prefix indicating the
number to the suffix -ane.
What is a substituent? - ANSWER -Any group attached to the parent chain.
What are alkyl groups? - ANSWER -Saturated hydrocarbon substituents. You drop the
-yl for -ane.
A one carbon substituent is a methyl group, four carbon is butyl.
What is a locant? - ANSWER -A number used to determine the suffix.
Describes the position of substituents.
What happens when two or more of the same type of substituents are present on the
parent chain? Like 3 methyl groups - ANSWER -Additional prefixes including the
number are added.
How would you describe finding 2,3 dimethylpentane? - ANSWER -It is a 5 carbon
chain, then it has substituents on numbers 2, 3 and those are methyl groups.
How are IUPAC systematic names put together? - ANSWER -Locant-(prefix)
substituentparent
If two or more different substituents are present on the parent chain then what
happens? - ANSWER -They are listed alphabetically. Ethyl before methyl
How are halogen atoms as substituents named? - ANSWER -Change the -ine to -o,
chlorine=chloro, bromine=bromo.
propyl or n-propyl - ANSWER -CH3CH2CH2
isopropyl - ANSWER -CH3CHCH3
Answers Graded A+
What are conformers? - ANSWER -Different shapes of molecules that are derived by
rotations of single bonds.
What does the Newman projection do? - ANSWER -It shows the conformation of
molecules when looking down a particular bond axis.
What is the difference in hydrogen placement between an eclipsed confirmation and a
staggered one? - ANSWER -The hydrogens do not overlap in staggered but they do in
eclipsed.
What are Alkanes? - ANSWER -They are saturated hydrocarbons because their
skeleton is only composed of C-C single bonds.
How can alkanes exist? - ANSWER -They can be linear, branched or exist in ring
formations called cycloalkanes.
Describe a higher/more complex alkane structure: - ANSWER -They will have more
carbons and/or increased structural diversity.
What is the general formula of Alkanes? - ANSWER -CnH2n+2
The names of the alkanes reflect? - ANSWER -The number of carbons present.
How many isomers does each alkane have from 1-10 - ANSWER -
1,1,1,2,3,5,9,18,35,75
Name the first ten prefix of alkanes: - ANSWER -Methane, ethane, propane, butane,
pentane, hexane, heptane, octane, nonane, decane.
As the molecular weight increases: - ANSWER -The number of isomers increase.
What does the suffix -ane mean? - ANSWER -Denotes a saturated hydrocarbon. It is
used for all acyclic saturated alkanes
What is nomenclature? - ANSWER -The naming of a molecular structure. Historically
they were named after their source, now they are systemic.
Why is nomenclature important? - ANSWER -Because we cannot remember all the
prefixes since a MF composed of carbons can have several different patterns of
connectivity.
, What is it meant by the systemic approach? - ANSWER -There are now methods of
naming molecules so that they all have unique names. You can then determine the
structure from only the name and vice-versa.
IUPAC rules for naming branced alkanes: - ANSWER -1. Find the parent name by
identifying the longest continuous chain of carbons.
2. Number the parent chain. (begin at the end of the chain nearest to the first branch.)
3. If there are two equally long continuous chains, select the one with most branches.
4. If the first branch point is the same distance, choose the one that gives the lowest
substituents.
5. If the substituents are both equidistant then choose the numbering so the substituent
goes with the higher alphabetic priority.
How are linear alkanes named? - ANSWER -By combining the prefix indicating the
number to the suffix -ane.
What is a substituent? - ANSWER -Any group attached to the parent chain.
What are alkyl groups? - ANSWER -Saturated hydrocarbon substituents. You drop the
-yl for -ane.
A one carbon substituent is a methyl group, four carbon is butyl.
What is a locant? - ANSWER -A number used to determine the suffix.
Describes the position of substituents.
What happens when two or more of the same type of substituents are present on the
parent chain? Like 3 methyl groups - ANSWER -Additional prefixes including the
number are added.
How would you describe finding 2,3 dimethylpentane? - ANSWER -It is a 5 carbon
chain, then it has substituents on numbers 2, 3 and those are methyl groups.
How are IUPAC systematic names put together? - ANSWER -Locant-(prefix)
substituentparent
If two or more different substituents are present on the parent chain then what
happens? - ANSWER -They are listed alphabetically. Ethyl before methyl
How are halogen atoms as substituents named? - ANSWER -Change the -ine to -o,
chlorine=chloro, bromine=bromo.
propyl or n-propyl - ANSWER -CH3CH2CH2
isopropyl - ANSWER -CH3CHCH3
