Orgo Chapter 4

How many carbon atoms are there in the longest continuous carbon chain in the structure shown?

6

Give the IUPAC name for the following compound.

8-ethyl-4-isopropyl-2,6-dimethyldecane

Match the value of the dihedral angle to the conformations shown.

A = 60 (degrees) B = 0 (degrees)

Select all the statements that correctly describe the procedure for drawing a Newman projection.

A circle is used to represent the back carbon. There will be 3 lines drawn directly to each C atom. A dot drawn at the center of the circle represents the front C. A Newman projection considers one C-C bond at a time.

In the chair conformation for cyclohexane, a larger substituent is more stable _______ in the position because this position has more space than the ______ position.

Blank 1: equatorial Blank 2: axial

Select all the statements that correctly describe the IUPAC rules for naming an alkane.

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.

Select all statements that correctly describe the stability of eclipsed and staggered conformers.

Eclipsed conformers possess torsional strain. Staggered conformers are lower in energy than eclipsed conformers.

True or false: When one cyclohexane chair conformation converts to the other through a ring-flip, substituents that were above the ring are now below the ring and vice versa.

False: A ring-flip interchanges up and down carbons and interconverts axial and equatorial bonds; however, a substituent always stays on the same side of the ring.

Select all statements that correctly describe the systematic naming of organic compounds.

The systematic name indicates the compound's chemical structure. The systematic naming of compounds is referred to as the IUPAC system of nomenclature.

Carbon substituents that are bonded to a long carbon chain are known as _____ groups.

alkyl

What type of strain is caused by the small internal angles of cyclopropane and cyclobutane?

angle strain

An increase in energy caused when tetrahedral bond angles deviate from the optimum angle of 109.5o is called _____ strain. This type of strain is found typically in _____.

angle; cycloalkanes

In a cyclohexane chair, substituents may be axial or equatorial, and may also be above or below the plane of the ring. In the structure shown, the Br atom is in a(n) _____ position and is _____ the plane of the ring and the CH3 group is in a(n) _____ position and is _____ the plane of the ring.

axial; above; equatorial; above

Match each structure in the diagram with its common name.

basketane = A churchane = B cubane = C housane = D

The most stable conformation for cyclohexane is the _____ conformation. In this conformation _____ strain is eliminated because all internal bond angles are equal to 109.5o. All bonds to hydrogen atoms on adjacent carbon atoms are _____ and therefore torsional strain is minimized.

chair; angle; staggered

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 in the conformation shown) the value of this angle is ________ degrees.

dihedral 0

Which of the following is a polycyclic alkane composed of 12 five-membered rings?

dodecahedrane

Rank the following conformations in order of increasing stability (less stable at the top of the list).

eclipsed staggered

Bulky substituents prefer to occupy a(n) ______ position in the cyclohexane chair conformation, since the substituent has more space.

equatorial

C-C σ 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

A staggered conformation in which two larger groups are 600 from each other is called a(n) ________ conformation, whereas a staggered conformation in which two larger groups are 180o from each other is called a(n) ________ conformation.

gauche anti

Which structure is identical to the given structure, and which is its stereoisomer?

identical = A stereoisomer = B

An alkane parent chain is always numbered to give the first substituent the _______ number. If the first substituent is the same distance from both ends the chain is numbered to give the _______ substituent the lowest possible number.

lowest; second

Classify the following pair of compounds. Select the single best answer.

not isomers

To name a simple cycloalkane, the number of carbon atoms in the ring gives the name and the prefix is added before this part of the name.

parent; cyclo

To name a simple cycloalkane, the number of carbon atoms in the ring gives the ________ name and the prefix ________ is added before this part of the name.

parent; cyclo-

Place the steps for naming an acyclic alkane in the correct order. Place the first step at the top of the list and the last step at the bottom of the list.

1. Find the parent carbon chain and add the suffix 2. Number the atoms in the parent carbon chain 3. name and number the substituents 4. Combine substituent names and numbers + parent + suffix

How many carbon atoms are there in the longest continuous carbon chain in the structure shown?

9

Which carbons in the chair conformation of cyclohexane (shown) are up carbons?

A, C, and E

Select the statement that correctly describes the carbon atoms of the cyclohexane chair shown in the diagram.

A, C, and E are up C's, whereas D and F are down C's.

Select all of the statements that correctly describe the chair conformation of cyclohexane.

All hydrogen atoms on adjacent carbon atoms are staggered. The bond angles are 109.50. Each carbon atom has one axial and one equatorial hydrogen atom.

Select the statements that correctly describe the changes which result from the ring-flip from one cyclohexane chair conformation to the other.

An axial substituent becomes equatorial. An equatorial substituent becomes axial. An up carbon atom becomes a down carbon atom.

A cyclohexane derivative can undergo a conformational change from one chair conformation to another through a ring-flip. What happens to the axial and equatorial bonds as a result of this conformational change?

Axial and equatorial bonds are interconverted.

Select all the statements that correctly describe the different conformations of a compound.

Conformations are different arrangements of atoms that are interconverted by rotation about single bonds. Conformations interconvert by rotation about σ bonds. The conformations of a compound are not all equally stable.

Select all the conformations of 2-methylbutane that will be energy maxima in a graph of dihedral angle vs. energy.

Conformer A Conformer D

_____ nomenclature is a set of rules used to assign a _____ name to a compound.

IUPAC; systematic

Select all the statements that correctly describe how to name a cycloalkane.

If there is an alkyl 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 the correct numbering system for the alkane shown.

Option A

Select the correct numbering system for the alkane shown.

Option C

Which one of the following options does NOT represent a conformer of propane, looking down the C2-C3 bond?

Option C

Select all the statements that correctly describe the "ring-flip" of a cyclohexane chair conformation.Select all the statements that correctly describe the "ring-flip" of a cyclohexane chair conformation.

The ring-flip represents a conformational change. A bond to H which is up remains up after the ring-flip. Axial and equatorial H atoms are interconverted during a ring-flip. A chair conformer is converted into another chair via a boat conformation.

Select the correct definition for steric strain.

Steric strain is an increase in energy caused by two atoms being forced too close to one another.

Select the structure that represents the stereoisomer of the compound shown.

Structure A

Match each structure to the chair conformation that is obtained by a ring-flip in each case.

Structure A --> Structure D Structure C --> Structure B

Select the correct structure for cis-1,2-dibromocyclopentane.

Structure B

Which of the following is the correct Newman projection for the staggered conformer of bromoethane?

Structure B

Structure A shows one chair conformation for bromocyclohexane. Select the structure that results from a ring-flip of Structure A.

Structure X

Select all the statements that correctly interpret the Newman projection shown.

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 how to number the parent chain of an alkane.

The chain is numbered to give the first substituent the lowest number. If the first substituent is the same distance from both ends, the chain is numbered to give the second substituent the lowest number.

Select all the statements that correctly describe how to draw the chair form of cyclohexane.

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."

True or false: Alkyl groups are formed by removing one hydrogen from an alkane.

True

Identify each marked substituent on the cyclohexane derivative shown according to its orientation.

a = axial and above the ring b = equatorial and above the ring c = equatorial and below the ring d = axial and below the ring

The most and least stable conformations of ethane are shown. Conformer A in which the 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.

staggered; eclipsed

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

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

Newman projections are given for two of the conformers of 2-methylbutane, drawn as viewed down the C2-C3 bond. In A the _____ strain is at a 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

Identify the stereoisomers shown according to the geometric relationship of the substituents.

trans isomer = structure A cis isomer = structure B