Compare the energies of cycloalkanes, and explain how their angle strain and torsional

Using the general molecular formula for alkanes: (a) Predict the molecular formula of the C28 straight-chain alkane. (b) Predict the molecular formula of the alkanes containing 44 carbon atoms with extensive branching

Name the following alkanes and haloalkanes. When two or more substituents are present, list them in alphabetical order. CH2 CH3 3 CHCH CH2 CH3 (a) CH3 CH Br CH2CH3 CH CH3 (b) (c) CH2CH(CH3) CH3 CH2 2 CH3 CH2 CH CH CH2 CH2 CH3 (d) CH3 CH3 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH CH3 CH CH3 CH

Write structures for the following compounds. (a) 3-ethyl-4-methylhexane (b) 3-ethyl-5-isobutyl-3-methylnonane (c) 4-tert-butyl-2-methylheptane (d) 5-isopropyl-3,3,4-trimethyloctane

Provide IUPAC names for the following compounds. (a) (CH3)2CHCH2CH3 (b) CH3C(CH3)2CH3 CH2CH3 CH3CH2CH2CH (c) CH(CH3)2 (d) CH3 CH2CH3 CH3 CH CH2 CH CH3 C(CH3)3 CH3CH2CHCHCH3 CH(CH3)2 (e) (f) CH3 CHCH2CH3 (CH3)3C CH CH2CH2CH3

All of the following names are incorrect or incomplete. In each case, draw the structure (or a possible structure) and name it correctly. (a) 3-ethyl-4-methylpentane (b) 2-ethyl-3-methylpentane (c) 3-dimethylhexane (d) 4-isobutylheptane (e) 2-bromo-3-ethylbutane (f) 2,3-diethyl-5-isopropylheptane

Give structures and names for (a) the five isomers of C6H14 (b) the nine isomers of C7H16

Draw the structures of the following groups, and give their more common names. (a) the (1-methylethyl) group (b) the (2-methylpropyl) group (c) the (1-methylpropyl) group (d) the (1,1-dimethylethyl) group (e) the (3-methylbutyl) group, sometimes called the isoamyl group

Draw the structures of the following compounds. (a) 4-(1,1-dimethylethyl)octane (b) 5-(1,2,2-trimethylpropyl)nonane (c) 3,3-diethyl-4-(2,2-dimethylpropyl)octane

Without looking at the structures, give molecular formulas for the compounds in Problem 3-8 (a) and (b). Use the names of the groups to determine the number of carbon atoms; then use the (2n+2) rule.

List each set of compounds in order of increasing boiling point. (a) hexane, octane, and decane (b) octane, (CH3)3CC(CH3)3, and CH3CH2C(CH3)2CH2CH2CH3

Draw Newman projections of the following molecules viewed from the direction of the blue arrows. H C H C Cl CH3 Br CH2CH3 (a) (b) H H Cl C C CH3 CH2CH3 Br (c) H CH3 H Br

Draw a graph, similar to Figure 3-9, of the torsional strain of 2-methylpropane as it rotates about the bond between C1 and C2. Show the dihedral angle and draw a Newman projection for each staggered and eclipsed conformation.

Draw a graph, similar to Figure 3-11, of the torsional energy of 2-methylbutane as it rotates about the \(\mathrm{C} 2-\mathrm{C} 3\) bond.

Draw a perspective representation of the most stable conformation of 3-methylhexane.

Give IUPAC names for the following compounds.

Draw the structure and give the molecular formula for each of the following compounds. (a) 1-ethyl-3-methylcycloheptane (b) isobutylcyclohexane (c) cyclopropylcyclopentane (d) 3-ethyl-1,1-dimethylcyclohexane (e) 3-ethyl-2,4-dimethylhexane (f) 1,1-diethyl-4-(3,3-dimethylbutyl)cyclohexane

Which of the following cycloalkanes are capable of geometric (cis-trans) isomerism? Draw the cis and trans isomers. (a) 3-ethyl-1,1-dimethylcyclohexane (b) 1-ethyl-3-methylcycloheptane (c) 1-ethyl-3-methylcyclopentane (d) 1-cyclopropyl-2-methylcyclohexane

Give IUPAC names for the following cycloalkanes. CH3 H H CH2CH2CH3 (a) (b) H C(CH3)3 H CH2CH3 (c) H CH3 H H3C

The heat of combustion of cis-1,2-dimethylcyclopropane is larger than that of the trans isomer. Which isomer is more stable? Use drawings to explain this difference in stability.

trans-1,2-Dimethylcyclobutane is more stable than cis-1,2-dimethylcyclobutane, but cis-1,3-dimethylcyclobutane is more stable than trans-1,3-dimethylcyclobutane. Use drawings to explain these observations.

The cyclohexane chair shown in Figure 3-22 has the headrest to the right and the footrest to the left. Draw a cyclohexane chair with its axial and equatorial bonds, showing the headrest to the left and the footrest to the right.

Draw 1,2,3,4,5,6-hexamethylcyclohexane with all the methyl groups (a) in axial positions. (b) in equatorial positions.

Draw a Newman projection, similar to Figure 3-25, down the C1-C6 bond in the equatorial conformation of methylcyclohexane. Show that the equatorial methyl group is also anti to C5. (Using your models will help.)

Table 3-6 shows that the axial–equatorial energy difference for methyl, ethyl, and isopropyl groups increases gradually: 7.6, 7.9, and 8.8 kJ/mol (1.8, 1.9, and 2.1 kcal/mol). The tert-butyl group jumps to an energy difference of 23 kJ/mol (5.4 kcal/mol), over twice the value for the isopropyl group. Draw pictures of the axial conformations of isopropylcyclohexane and tert-butylcyclohexane, and explain why the tert-butyl substituent experiences such a large increase in axial energy over the isopropyl group.

Draw the most stable conformation of (a) ethylcyclohexane. (b) 3-isopropyl-1,1-dimethylcyclohexane. (c) cis-1-tert-butyl-4-isopropylcyclohexane.

Name the following compounds. Remember that two up bonds are cis; two down bonds are cis; one up bond and one down bond are trans.

(a) Draw both chair conformations of cis-1,4-dimethylcyclohexane, and determine which conformer is more stable. (b) Repeat for the trans isomer. (c) Predict which isomer (cis or trans) is more stable.

Use your results from Problem 3-27 to complete the following table. Each entry shows the positions of two groups arranged as shown. For example, two groups that are trans on adjacent carbons (trans-1,2) must be both equatorial (e,e) or both axial (a,a).

Draw the two chair conformations of each of the following substituted cyclohexanes. In each case, label the more stable conformation. (a) cis-1-ethyl-2-methylcyclohexane (b) trans-1,2-diethylcyclohexane (c) cis-1-ethyl-4-isopropylcyclohexane (d) trans-1-ethyl-4-methylcyclohexane

Draw the most stable conformation of (a) cis-1-tert-butyl-3-ethylcyclohexane. (b) trans-1-tert-butyl-2-methylcyclohexane. (c) trans-1-tert-butyl-3-(1,1-dimethylpropyl)cyclohexane

Name the following compounds.

Use your models to do a chairchair interconversion on each ring of the conformation of cis-decalin shown in Figure 3-27. Draw the conformation that results.

Given the IUPAC name or common name of an alkane, draw the structure and give the molecular formula. (Problems 3-36, 37, 41, and 49)

Draw isomers of alkanes and cycloalkanes, and use the IUPAC rules to name alkanes, cycloalkanes, and bicyclic alkanes. (Problems 3-33, 34, 35, 39, 43, and 52)

Explain and predict trends in the physical properties of alkanes.

Use Newman projections to compare conformational energies and predict the most stable conformation. Show how the torsional energy varies as the dihedral angle changes.

Compare the energies of cycloalkanes, and explain how their angle strain and torsional strain combine to give the total ring strain. (Problem 3-45)

Draw accurate cyclohexane chair conformations. Place axial and equatorial groups in their proper positions with correct bond angles.

Predict the most stable conformations of mono and disubstituted cyclohexanes by placing the larger groups in equatorial rather than axial position.

(a) There are 18 isomeric alkanes of molecular formula C8H18. Draw and name any eight of them. (b) Draw and name the six isomeric cyclopentanes of molecular formula C7H14. These will include four constitutional isomers, of which two show geometric (cis-trans) stereoisomerism.

Which of the following structures represent the same compound? Which ones represent different compounds? (g) Name the structures given in Problem 3-34, parts (a), (c), (e), and (f). Make sure your names are the same for structures that are the same, and different for structures that are different.

(a) Draw and name the five cycloalkane structures of formula C5H10. Can any of these structures give rise to geometric (cis-trans) isomerism? If so, show the cis and trans stereoisomers. (b) Draw and name the eight cycloalkane structures of formula C6H12 that do not show geometric isomerism. (c) Draw and name the four cycloalkanes of formula C6H12 that do have cis-trans isomers.

Draw the structure that corresponds with each name. (a) 3-ethyloctane (b) 4-isopropyldecane (c) sec-butylcycloheptane (d) 2,3-dimethyl-4-propylnonane (e) 2,2,4,4-tetramethylhexane (f) trans-1,3-diethylcyclopentane (g) cis-1-ethyl-4-methylcyclohexane (h) isobutylcyclopentane (i) tert-butylcyclohexane (j) pentylcyclohexane (k) cyclobutylcyclohexane (l) cis-1-bromo-3-chlorocyclohexane

Each of the following descriptions applies to more than one alkane. In each case, draw and name two structures that match the description. (a) an isopropylheptane (b) a diethyldecane (c) a cis-diethylcyclohexane (d) a trans-dihalocyclopentane (e) a (2,3-dimethylpentyl)cycloalkane (f) a bicyclononane

Write structures for a homologous series of alcohols (ROH) having from one to six carbons.

Give the IUPAC names of the following alkanes. (a) CH3C(CH3)2CH(CH2CH3)CH2CH2CH(CH3)2 (b) CH3CH2 CH CHCH3 CH2CH2 CH3 CH CHCH3 CH3 CH3 (c) (d) CH2CH3 CH2CH3 CH3 (e) CH2CH2CH3 CH2CH3 (f) (g) C(CH2CH3)3 (h) CH2CH3 CH(CH3)2

Construct a graph, similar to Figure 3-11, of the torsional energy of 3-methylpentane along the \(\mathrm{C} 2-\mathrm{C} 3\) bond. Place C2 in front, represented by three bonds coming together in a Y shape, and C3 in back, represented by a circle with three bonds pointing out from it. Define the dihedral angle as the angle between the methyl group on the front carbon and the ethyl group on the back carbon. Begin your graph at the \(0^{\circ}\) dihedral angle and begin to turn the front carbon. Show the Newman projection and the approximate energy at each \(60^{\circ}\) of rotation. Indicate which conformations are the most stable (lowest energy) and the least stable (highest energy).

The following names are all incorrect or incomplete, but they represent real structures. Draw each structure and name it correctly. (a) 2-ethylpentane (b) 3-isopropylhexane (c) 5-chloro-4-methylhexane (d) 2-dimethylbutane (e) 2-cyclohexylbutane (f) 2,3-diethylcyclopentane

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. (a) octane or 2,2,3-trimethylpentane (b) nonane or 2-methylheptane (c) 2,2,5-trimethylhexane or nonane

There are eight different five-carbon alkyl groups. (a) Draw them. (b) Give them systematic names. (c) In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom bonded to the main chain.

Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. (a) 3-methylpentane about the C2¬C3 bond (b) 3,3-dimethylhexane about the C3¬C4 bond

(a) Draw the two chair conformations of cis-1,3-dimethylcyclohexane, and label all the positions as axial or equatorial. (b) Label the higher-energy conformation and the lower-energy conformation. (c) The energy difference in these two conformations has been measured to be about 23 kJ (5.4 kcal) per mole. How much of this energy difference is due to the torsional energy of gauche relationships? (d) How much energy is due to the additional steric strain of the 1,3-diaxial interaction? 3-46 Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable. (a) cis-1-ethyl-2-isopropylcyclohexane (b) trans-1-ethyl-2-isopropylcyclohexane (c) cis-1-ethyl-3-methylcyclohexane (d) trans-1-ethyl-3-methylcyclohexane (e) cis-1-ethyl-4-methylcyclohexane (f) trans-1-ethyl-4-methylcyclohexane 3-47 Using what you know about the conformational energetics of substituted cyclohexanes, predict which of the two decalin isomers is more stable. Explain your reasoning. 3-48 Convert each Newman projection to the equivalent lineangle formula, and assign the IUPAC name.

Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable. (a) cis-1-ethyl-2-isopropylcyclohexane (b) trans-1-ethyl-2-isopropylcyclohexane (c) cis-1-ethyl-3-methylcyclohexane (d) trans-1-ethyl-3-methylcyclohexane (e) cis-1-ethyl-4-methylcyclohexane (f) trans-1-ethyl-4-methylcyclohexane

Using what you know about the conformational energetics of substituted cyclohexanes, predict which of the two decalin isomers is more stable. Explain your reasoning.

Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name.

Draw Newman projections along the C3C4 bond to show the most stable and least stable conformations of 3-ethyl-2,4,4-trimethylheptane.

Conformational studies on ethane-1,2-diol (\(HOCH_2 - CH_2OH\)) have shown the most stable conformation about the central C¬C bond to be the gauche conformation, which is 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation. Draw Newman projections of these conformers, and explain this curious result.

The most stable form of the common sugar glucose contains a six-membered ring in the chair conformation with all the substituents equatorial. Draw this most stable conformation of glucose.

This is a Newman projection of a substituted cyclohexane. (a) Draw the equivalent chair form. (b) Draw the equivalent structure using wedge and dash notation on a cyclohexane hexagon. (c) Give the IUPAC name.