Chapter 3 Flashcards
What are hydrocarbons?
Compounds composed of only carbon and hydrogen
What are saturated hydrocarbons?
Hydrocarbons containing ONLY C-C and C-H single bonds
What is an Alkane/Aliphatic Hydrocarbon?
A saturated hydrocarbon whose C are arranged in an OPEN chain
Describe the structure of Alkanes
Tetrahedral geometry (all 109.5 degrees) where all carbons are sp3 hybridized
What is the general formula all Alkanes follow?
C nH 2n+2
What are constitutional isomers?
Compounds with the same molecular formula but different connectivity between atoms
In IUPAC nomenclature what does the suffix “-ane” mean
The molecule is an Alkane with the “prefix specified” number of carbons
How can you remember the IUPAC prefixes?
“Merry Elk Prosper But their Penthouse is Hexed. Helping, the Octopus Notes Deception.”
In IUPAC the parent name represents the ___________ while the substituent is the ______________
the longest carbon chain
a group bonded to the parent chain
In IUPAC naming, in a multi-structure hydrocarbon which name comes first?
substituent first + parent name second
When naming Alkanes with one substituent, provide the number carbon it is on, number from . . .
Numbering from the direction that would give that specific position the lowest number
If there are two or more IDENTICAL substituents, number the parent chain from the end that ____________. The number of times the substituent occurs is indicated by prefixes . . .
gives the lower number to the substituent encountered first and provide the numbered locations in the compound name separated by a common
di-, tri-, tetra-, etc
If there are two or more DIFFERENT substituents . . . and number the parent chain in the direction that . . .
list them in alphabetical order
gives the lower number to the substituent encountered first
When alphabetizing substituents, what is NOT included?
The prefixes di-, tri-, tetra-
How are carbons specifically classified?
What is the general formula for cycloalkanes and the most common forms?
C nH 2n
5 and 6 member rings are the most common
Describe the nomenclature for cycloalkanes:
1. Prefix?
2. 1 substituent?
3. 2 substituents?
4. 3+ substituents?
What are the 3 common infixes for IUPAC
-an- all single bonds
-en- one or more double bonds
-yn- one or more triple bonds
What are the 5 common suffixes for IUPAC
-e hydrocarbon
-ol alcohol
-al aldehyde
-one ketone
-oic acid carboxylic acid
Draw the structure and give the formulas for:
methyl
ethyl
propyl
Draw the structure and give the formulas for:
Isopropyl
Sec-butyl
Tert-butyl
What does the prefix, infix, and suffix tell us about an IUPAC compound?
prefix - # of C in the parent
infix - nature of the C-C bonds
suffix - class of the compound
What is conformation?
Any 3D arrangement of atoms in a molecule that results from a rotation of a single bond
Describe “staggered” conformation
A conformation about a C-C single bond where the atoms on one carbon are as far apart as possible from the atoms on the adjacent carbon
Describe “eclipsed” conformation
A conformation about a C-C single bond in which the atoms on one carbon are as close as possible to the atoms on the adjacent carbon
What is the most stable (lowest energy) conformation for an alkane?
fully staggered, “zig-zag”
Describe torsional strain/eclipsed interaction strain
Strain that arises when nonbonding atoms separated by 3 bonds are forced from a staggered conformation to an eclipsed conformation
Describe angle strain
Strain that arises when a bond angle is either compressed or expanded compared to its optimal value
In planar cyclopentane all C-C bond angles are ______, which is only slightly different from the ideal _____ angle. Thus there is . . .
108
109.5
little angle strain between carbons
In planar cyclopentane there are 10 fully eclipsed ____________ created a great deal of _________ strain.
C-H bonds
torsional
How does a planar cyclopentane molecule reduce the torsional strain created by the eclipsed C-H bonds?
It puckers to an “envelope” conformation so eclipsed interactions are reduced but angle strain is increased slightly
Like cyclopentane, cyclohexane puckers into its most stable “______” conformation where all bond angles are roughly ________ and all bonds on adjacent carbons are __________
chair
109.5
staggered
How do you draw cyclohexane chair conformations?
Note that the “direction” of both axial bonds and equatorial bonds alternates between each carbon. If the first equatorial you draw is “down” the next must be “up”
Cyclohexane has another, less stable conformation known as the “______” in which carbons 1 and 4 are __________________
boat
bent towards each other
Why is the cyclohexane boat less stable than the chair?
Torsional strain is created by the 4 sets of eclipsed hydrogens, steric strain (nonbonding interactional strain) is created by one set of flagpole interactions
In chain cyclohexane there are _______________ conformations. These conformations interconvert via a __________ conformation. All C-H bonds that equatorial in the first chair become . . .
2 equivalent
boat
axial in the alternative chair, and vise versa
When are alternative chair conformations NOT equivalent?
If there is a group (such as a methyl) that is interconverting between axial and equatorial across conformations
Chair conformations with “heavy” groups like methyls are MOST stable when those groups are in what position?
equatorial
Cis-trans isomers are the same in what ways? What are they not?
Same molecular formula
Same connectivity of their atoms (NOT constitutional)
An arrangement of atoms in space that cannot be interconverted by rotating (NOT conformers)
A cyclopentane ring should be treated as a ___________ viewed from an angle rather than a pucker when drawing cis-trans isomers.
flat pentagon
Draw cis-1,2-dimethylcyclopentane and trans-1,2-dimethylcyclopentane
A cyclohexane ring can be treated as a ___________ viewed from an angle for cis-trans isomers OR in _________ conformation
planar hexagon
chair
Draw planar cis-1,4-dimethylcyclohexane and trans-1,4-dimethylcyclohexane
Draw chair trans-1,4-dimethylcyclohexane. What are the two possible conformations? Which is more stable?
Draw chair cis-1,4-dimethylcyclohexane. What are the two possible conformations? Which is more stable?
Alkanes are ________ compounds and have only weak interactions between their molecules. _____________ forces are weak intermolecular interactions resulting from temporary induced ________
nonpolar
Dispersion
dipoles
Describe the state of 1-4C, 5-17C, and 18+C Alkanes at room temperature
_________ is the basis for the use of alkanes as energy sources for heat and power. The ___________________ is the heat released when one mol of a substance is oxidized into __________ and _________
Oxidation
Heat of combustion
CO2 , H2O
Liquid AND solid alkenes _______ on water
float
Draw and compare
- propyl v. isopropyl
- butyl v. sec-butyl
- tert-butyl v. isobutyl
