Organic Chemistry I Lecture Chapter 4 Learnsmart
What statement correctly describes the relationship between structures A and B A) CH3~CH2~CH2~CH3 CH3 | B) CH3~CH2~CH2 "A and B are different because their spatial arrangement of their atoms is different" "A and B are identical because B is produced by the rotation of a single bond in A" "A and B are different compounds because B is formed by breaking a bond and forming a new one"
A and B are identical because B is produced by the rotation of a single bond in A
How many carbon atoms are there in the longest continuous carbon chain in the structure? CH2~CH3 | CH2~CH2~CH~CH2~CH2~CH3 | H3C~CH | CH3
9
Which alkane uses the correct numbering system CH3 1 2 |3 4 5 6 A) H3C~CH~CH~CH2~CH~CH3 | | CH3 CH3 CH3 6 5 |4 3 2 1 B) H3C~CH~CH~CH2~CH~CH3 | | CH3 CH3 3CH3 1 2 |4 6 7 9 C) H3C~CH~CH~CH2~CH~CH3 | | 3CH3 8CH3 CH3 5 |4 3 2 H3C~CH~CH~CH2~CH~CH3 | | 6 CH3 1 CH3
A
Select all the structures that represent structural isomers (constitutional isomers) of 2-methylpentane CH3 | A) CH3~CH2~CH~CH2~CH3 CH3 CH3 | | B) CH3~CH~CH2~CH2 CH3 CH3 | | C) CH3~CH~CH~CH3 CH3 | D) CH3~CH2~CH2~CH~CH3
A and C
Which structures are branched alkanes CH | A) CH3~CH2~CH~CH2~CH3 B) CH2~CH2~CH2~CH2 | | CH3 CH3 C) CH3~CH2~CH2~CH2CH3 D) | /\/\
A and D
12C
Dodecane
In an alkane all C atoms are surrounded by ___________ individual groups and are therefore ___________ hybridized with a ______________ geometry
Four sp3 Tetrahedral
C-C sigma bonds allow ____________ rotation about the bond, which places the substituents on the carbon atoms into different 3-D orientations with respect to each other. These different 3-D arrangements are called ________
Free Conformations
An increase in energy caused when tetrahedral bond angles deviate from optimum angle of 109.5* is called _____ strain. This type of strain is found typically in _____
Angle Cycloalkanes
Alkanes contain only C-C and C-H bonds, which are _____. As a result, they exhibit only van der _____ forces, which are much _____ than dipole-dipole forces. The melting and boiling points of these compounds are therefore _____ than the melting and boiling points of polar compounds of comparable size.
Nonpolar Waals Weaker Lower
8C
Octane
15C
Pentadecane
5C
Pentane
3C
Propane
An alkyl group is named according to the number of C atoms it contains. An alkyl group with three carbon atoms joined in a straight chain is called a(n) _______ group, whereas a methyl group has ______ carbon atom(s)
Propyl 1
20C
icosane
What are the two types of alkanes
Acyclic Cyclic
1C
Methane
14C
Tetradecane
13C
Tridecane
CH3 CH2CH3 \\ | // / || \
No torsional strain, some steric strain
9C
Nonane
Define steric strain
An increase in energy caused by two atoms being forces too close to one another
What type of strain is caused by the small internal angles of cyclopropane and cyclobutane
Angle
Select all the statements that correctly describe how to number the parent chain of an alkane "The chain is numbered from left to right" "The chain is numbered to give the highest number to the first substituent" "If the first substituent is the same distance from both ends, the chain is numbered to give the second substituent the lowest number" "The chain is numbered to give the first substituent the lowest number" "The chain is numbered so that the lowest number is given to the substituent that is first alphabetically"
"If the first substituent is the same distance from both ends, the chain is numbered to give the second substituent the lowest number" "The chain is numbered to give the first substituent the lowest number"
Constitutional or structural isomers have _________ molecular formulas and ____________ connectivities of their atoms
Identical Different
11C
Undecane
Select all the statements that correctly describe how to name a cycloalkane "The name of a cycloalkane ends with the suffix -cyclane" "If there is an alkane chain containing more C atoms than there are in the ring, the ring is named as a cycloalkyl substituent" "The parent name is given by the number of carbon atoms in the ring" "If there is a single substituent on the ring there is no need to specify its position" "For a ring with two different substituents, the ring is numbered to give the substituent with the least number of C atoms the lowest possible number"
"If there is an alkane chain containing more C atoms than there are in the ring, the ring is named as a cycloalkyl substituent" "The parent name is given by the number of carbon atoms in the ring" "If there is a single substituent on the ring there is no need to specify its position"
Select all the statements that correctly interpret the Newman projection shown a-> H H H \ || / //| \\ b->H H CL "The Cl atom is attached to the front carbon atom" "The hydrogen marked "b" is on the back atom" "This compound has a total of 3 carbon atoms" "The hydrogen marked "a" is on the back carbon atom
"The Cl atom is attached to the front carbon atom" "The hydrogen marked "a" is on the back carbon atom
Select all the statements that correctly describe the different conformations of a compound "The conformations of a compound are not all equally stable" "Conformations are different arrangements of atoms that are interconverted by rotation about single bonds" "Conformations are different compounds with different physical properties" "Conformations interconvert by rotation about sigma bonds"
"The conformations of a compound are not all equally stable" "Conformations are different arrangements of atoms that are interconverted by rotation about single bonds" "Conformations interconvert by rotation about sigma bonds"
Select all the statements that correctly describe the physical properties of alkanes "The melting points of normal alkanes generally increase as the number of C atoms in the chain increases" "The boiling point of alkane isomers increases with branching in the chain" "Alkanes are nonpolar compounds" "Alkanes with more than 5 carbons tend to be soluble in water" "Alkanes have lower boiling points than polar compounds of comparable size"
"The melting points of normal alkanes generally increase as the number of C atoms in the chain increases" "Alkanes are nonpolar compounds" "Alkanes have lower boiling points than polar compounds of comparable size"
Select all the statements that correctly describe the IUPAC rules for naming an alkane "The prefix tri is used to indicate that there are three identical alkyl groups attached to the longest chain" "The parent chain is numbered from left to right" "Each substituent must be numbered, even if there are two or more of the same group in the compound" "The parent name is obtained by finding the longest continuous carbon chain"
"The prefix tri is used to indicate that there are three identical alkyl groups attached to the longest chain" "Each substituent must be numbered, even if there are two or more of the same group in the compound" "The parent name is obtained by finding the longest continuous carbon chain"
Select all the statements that correctly describe how to draw the chair form of cyclohexane "The 3 upper carbon atoms on a chair conformation are in front of the plane" "Axial bonds on up carbon atoms point down" "To draw the carbon skeleton, draw two wedges joined by a set of parallel lines" "If the axial hydrogen on a particular carbon is up the equatorial hydrogen is down"
"To draw the carbon skeleton, draw two wedges joined by a set of parallel lines" "If the axial hydrogen on a particular carbon is up the equatorial hydrogen is down"
/ | | /\/\/\ |
2,5,6-trimethyloctane
| /\/\/\/\ |
2,7-dimethylnonane
| /\/\/\/\ |
3,4-dimethylnonane
Select the alkane name that has the correct format 2-methyl-3-ethyl-6-methylheptane 2,6-dimethyl-3-ethylheptane 3-ethyl-2,6-dimethylheptane 3-ethyl-2,6-dimethyl-heptane
3-ethyl-2,6-dimethylheptane
\ / | | \/\/\/\
3-ethyl-7-methylnonane
/\/ | | \/\/\/
5-ethyl-3-methylnonane
Place the following alkanes in order of increasing boiling point, based on their structures. A) /\/\ B) \/\/\/ | \/ C) /\/\/
A<C<B
Any carbon substituent formed by removing one hydrogen from an alkane is called a(n)_____ group
Alkyl
Eclipsed conformation
Bonds on adjacent C atoms are aligned
Staggered conformation
Bonds on one C bisect the bond angles on the adjacent C atom
4C
Butane
tert-butyl
CH3 | CH3~C- | CH3
isobutyl
CH3 | HC~CH2- | CH3
sec-butyl
CH3~CH~CH2~CH3 |
isopropyl
CH3~CH~CH3 |
The most stable conformation for cyclohexane is the _____ conformation. In this conformation _____ strain is eliminated because all internal bond angles are equal to 109.5*. All bonds to hydrogen atoms on adjacent carbon atoms are ______ and therefore torsional strain is minimized
Chair Angle Staggered
What is the molecular formula of cyclic alkanes
CnH2n
What is the molecular formula of acyclic alkanes
CnH2n+2
A cycloalkane is named by adding the prefix ______ to the name of the acyclic alkane that has the same number of ________ atoms
Cyclo Carbon
10C
Decane
The angle that separates a bond on one atom from a bond on an adjacent atom is called a _____ angle. For a pair of eclipsed bonds (as shown in the conformation shown) the value of this angle is _____ degrees
Dihedral 0
2C
Ethane
7C
Heptane
6C
Hexane
The gauche conformation of butane is _____ in energy and _____ stable than the anti conformation because the gauche conformation is destabilized by the ______ strain that results from the proximity of the CH3 groups
Higher Less Steric
|| | // /\ \\ CH3 CH2CH3
Maximal torsional and steric strain
CH2CH3 || | // /\ \\ H3C
Maximal torsional strain, no steric strain
A CH2 group is also called a __________ group
Methylene
If an alkane has two different chains of equal length, the longest continuous chain with the ____ substituents is selected as the parent chain
Most
CH3 \\ | // / || \ CH2CH3
No torsional strain, no steric strain
Acyclic alkanes are termed _______ hydrocarbons because they have the maximum number of H atoms per C atom. A cycloalkane with one ring has _____ fewer hydrogen atoms than an acyclic alkane with the same number of carbon atoms
Saturated Two
In which conformation, staggered or eclipsed is 1-chloroethane more stable
Staggered
The most stable conformations of ethane are shown. Conformer A in which C-H bonds on one carbon bisect the H-C-H bond angle on the adjacent carbon is called a _____ conformation. B is the _____ conformation, in which the C-H bonds of one carbon are directly aligned with the C-H bonds on the adjacent carbon \|/ /|\Conformer A || //\\Conformer B
Staggered Eclipsed
Rank the following conformations in order of stability Eclipsed Staggered
Staggered > Eclisped
An increase in energy that results from atoms being forced too close to one another is called _____ strain, while an increase in energy caused by eclipsing interactions is called _____ strain
Steric Torsional
How are alkanes named
Straight-chain alkanes are named according to the number of C atoms in the chain
The functional group present in an organic molecule is indicated by the _____ of the name whereas the _____ indicates the identity, location, and number of substituents attached to the carbon chain
Suffix Prefix
How are cycloalkanes with more than 3 C atoms able to reduce both angle and torsional strain
They are puckered instead of being flat
The type of strain that results from repulsion between the electrons in eclipsed sigma bonds is called _____ strain
Torsional
Newman projections are given two of the conformers of 2-methylbutane, drawn as viewed down the C2-C3 bond. In A the _____ strain is at maximum due to the eclipsing of bonds. In B this strain is minimized but there is still _____ strain due to the proximity of the bulky CH3 groups that are _____ to each other
Torsional Steric Gauche
True or False: Alkanes exhibit only weak van der Waals intermolecular forces
True
True or False: Alkyl groups are formed by removing one hydrogen from an alkane
True
