Chapter 3 - Structure And Stereochemistry Of Alkanes Flashcards
General formula of Alkanes
CnH2n+2
A series of compounds that differ only in the number of methylene groups is known as ___________
Homologous series
What does the prefix n mean in n-butane?
Short for normal, meaning straight chain
What does the prefix iso- mean?
Methyl branch is on next-to-last carbon in the chain
IUPAC Naming Rules
- Find the longest continuous chain and use the name as the base
- Number the longest chain beginning with the end of chain nearest a substituent
- Name the groups attached to the longest chain as alkyl groups, give the location of each alkyl group by the number of the main chain carbon which it is attached (always in alphabetical order regardless of position)
When there are two longest chains of equal length, use the chain __________
With the greatest number of substituents
One carbon alkyl group
Methyl (-CH3)
Two carbon alkyl group
Ethyl (CH3-CH2-)
Three carbon straight chain alkyl group
Propyl group (CH3-CH2-CH2-)
Isopropyl group
3 carbons, but a CH3 group is attached to the second carbon going upward
Four carbon straight chain alkyl group
Butyl (CH3-CH2-CH2-CH2-)
When two or more of the same substituents are present use ______
Prefixes (di-, tri-, tetra-)
When two or more of the of the same alkyl substituents are present use prefixes but _________
Don’t use the prefixes while alphabetizing the names of the substituents
Isobutyl group
CH3 group attached to the second carbon in a 3 carbon chain
Sec-butyl group
CH3 group on the third carbon in a three carbon chain
Tert-butyl group
Two CH3 groups on the second carbon in a 2 carbon chain
Primary carbon
One substituent and two hydrogens attached
Secondary carbon
Two substituents and one hydrogen attached
Tertiary carbon
Three substituents attached to the carbon
Methane has a hybridization of ___ and angles of ____
Sp3, 109.5 degrees
Ethane has hybridization of ____ and rotation about the _____ sigma bond
Sp3, C-C
______ are different arrangements of atoms caused by rotation about a single bond
Conformations
Eclipsed conformation is ____ in energy
Highest
Staggered conformation is _____ in energy
Lowest
Gauche conformation has a ____ angle between the methyl groups
60 degree
Totally eclipsed conformation is ____ in energy because ____ groups are in alignment
Highest, methyl
Anti conformation occurs when the bond angle between CH3 groups are ________
180 degrees apart
Anti conformations are ______ in energy
Lowest
Steric strain occurs when
The two end methyl groups are so close together that their electron clouds experience a strong repulsion
General formula of cycloalkanes
CnH2n
When naming cycloalkanes if only one alkyl group is present, then ___________
No number is necessary
In cycloalkanes cis means
Groups on the same face
In cycloalkanes trans means
Groups on opposite faces
Smaller rings demand bond angles _____ than 109.5 degrees, producing _______
Smaller, angle strain
Torsional strain arises when _________
All bonds are eclipsed
Heat of combustion is the
Amount of heat released when a compound is burned with an excess of oxygen in a sealed container
Cyclic compounds with >= 4 carbons adopt ____________ to relieve ring strain
Nonplanar conformations
The conformation of cyclopentane is slightly folded, like the shape of ___________
Open envelope
The _____ conformation is the most stable conformational isomer of cyclohexane
Chair
The chair conformation has no _____ strain or _____ strain
Torsional, angle
“Flagpole” hydrogens ________
Project towards each other adding additional strain
Axial bonds are directed ______ to the axis of the ring
Vertically parallel
Equatorial bonds are directed ______ toward the equator of the molecule
Outward
In chair-chair interconversion all axial substituents become _______ and vice versa
Equatorial
In chair-chair interconversion all substituents pointing up originally ____________
Remain pointing up
The axial substituent interferes with _______ on C3 and C5
Axial hydrogens
Cis-1,3-dimethylcyclohexane can have both methyl groups in ____ or _____ positions
Axial, equatorial
Trans-1,3-dimethylcyclohexane have ____ axial and ___ equatorial methyl groups
1,1
Fused rings share _____ carbon atoms and the bond between them
Two adjacent
Bridged rings share ______ carbon atoms and one or more carbon atoms between them
Two nonadjacent
Spirocyclic compounds share __________
Only one carbons
