Organic Compounds: Alkanes and Their Stereochemistry

Question: Sight along the C2-C3 bond of 2,3-dimethylbutane, and draw a Newman projection of the most stable conformation.

Identify the functional groups in the following model of arecoline, a veterinary drug used to control worms in animals. Convert the drawing into a line-bond structure and a molecular formula (red 5 O, blue 5 N).

Draw structures of the five isomers of C₆H₁₄.

Propose structures that meet the following descriptions:

(a) Two isomeric esters with the formula C₅H₁₀O₂

Propose structures that meet the following descriptions:

 (b) Two isomeric nitriles with the formula C₄H₇N

Propose structures that meet the following descriptions:

 (c) Two isomeric disulfides with the formula C₄H₁₀S₂

How many isomers are there with the following descriptions?

(b) Bromoalkanes with the formula C₄H₉Br

How many isomers are there with the following descriptions?

(a) Alcohols with the formula C₃H₈O

Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary

a)

Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary:

b)

Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary:

C)

Identify the hydrogen atoms on the compounds shown in Problem 3-8 as primary, secondary, or tertiary.

Draw the eight 5-carbon alkyl groups (pentyl isomers).

Draw structures of alkanes that meet the following descriptions:

 (c) An alkane that has one quaternary and one secondary carbon

Draw structures of alkanes that meet the following descriptions:

(a) An alkane with two tertiary carbons

Draw structures of alkanes that meet the following descriptions:

 (b) An alkane that contains an isopropyl group

Question: Give the IUPAC name for the following hydrocarbon, and convert the drawing into a skeletal structure.

Give IUPAC names for the following compounds:

(a)The three isomers of  C₅H₁₂

Question: Give IUPAC names for the following compounds:

Give IUPAC names for the following compounds:

Give IUPAC names for the following compounds:

Draw structures corresponding to the following IUPAC names:

(a) 3, 4-Dimethylnonane

Draw structures corresponding to the following IUPAC names:

(b) 3-Ethyl-4,4-dimethylheptane

Draw structures corresponding to the following IUPAC names:

(c) 2,2-Dimethyl-4-propyloctane

Draw structures corresponding to the following IUPAC names:

(d) 2,2,4-Trimethylpentane

Name the eight 5-carbon alkyl groups you drew in Problem 3-7.

Question: Make a graph of potential energy versus angle of bond rotation for propane,and assign values to the energy maxima.

Sight along the C2-C1 bond of 2-methylpropane (isobutane). 

(b) Draw a Newman projection of the least stable conformation.

Sight along the C2-C1 bond of 2-methylpropane (isobutane).

(a) Draw a Newman projection of the most stable conformation.

Sight along the C2-C1 bond of 2-methylpropane (isobutane). 

(c) Make a graph of energy versus angle of rotation around the C2-C1 bond.

Sight along the C2-C1 bond of 2-methylpropane (isobutane). 

(d) Assign relative values to the maxima and minima in your graph, given that

An eclipsing interaction costs 4.0 kJ/mol and an $\mathbf{H}\leftrightarrow {\mathbf{CH}}_{\mathbf{3}}$ eclipsing

Interaction costs 6.0 kJ/mol.

Draw a Newman projection along the C2 -C3 bond of the following conformation of 2,3-dimethylbutane, and calculate a total strain energy:

Predict the hybridization of the carbon atom in each of the following

Functional groups:

(b) Nitrile

Predict the hybridization of the carbon atom in each of the following  Functional groups:

(c) Carboxylic acid

Propose structures for the following:

(a) A ketone, ${\mathbf{C}}_{\mathbf{4}}{\mathbf{H}}_{\mathbf{8}}\mathbf{O}$

Draw compounds that contain the following:

1. A primary alcohol
2. A tertiary Nitrile
3. A secondary Thiol
4. Both primary and secondary alcohols
5. An isopropyl group
6. A quaternary carbon

Draw a compound that:

1. Has only primary and tertiary carbons
2. Has no secondary or tertiary carbons
3. Has four secondary carbons

Draw  a compound that:

1. Has nine primary hydrogens
2. Has only primary hydrogens

Draw structures for the following:

1. 2-Methylheptane
2. 4-ethyl-2,2-dimethylhexane
3. 4-ethyl-3,4-dimethyloctane
4. 2,4,4-Trimethylheptane
5. 3,3-Diethyl-2,5-Dimethylnonane
6. 4-Isopropyl-3-methylheptane

Formaldehyde, ${\mathrm{H}}_2\mathrm{C}=\mathrm{O}$, is known to all biologists because of its usefulness as a tissue preservative. When pure, formaldehyde trimerizes to give trioxane, ${\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{O}}_3$, which, surprisingly enough, has no carbonyl groups. Only one monobromo derivative (${\mathrm{C}}_3{\mathrm{H}}_5{\mathrm{BrO}}_3$) of trioxane is possible. Propose a structure for trioxane.

Question: The barrier to rotation about the C-C bond in bromoethane is 15 kJ/mol (3.6 kcal/mol). 

(a) What energy value can you assign to an H←→Br eclipsing interaction? 

(b) Construct a quantitative diagram of potential energy versus bond rotation for bromoethane.

Increased substitution around a bond leads to increased strain. Take the four substituted butanes listed below, for example. For each compound, sight along the C2–C3 bond and draw Newman projections of the most stable and least stable conformations. Use the data in Table 3-5 to assign strain-energy values to each conformation. Which of the eight conformations is most strained? Which is least strained? 

(a) 2-Methylbutane 

(b) 2,2-Dimethylbutane 

(c) 2,3-Dimethylbutane 

(d) 2,2,3-Trimethylbutane

The cholesterol-lowering agents called statins, such as simvastatin (Zocor) and pravastatin (Pravachol), are among the most widely prescribed drugs in the world, with annual sales estimated at approximately $25 billion. Identify the functional groups in both, and tell how the two substances differ.

In the next chapter we’ll look at cycloalkanes—saturated cyclic hydrocarbons—and we’ll see that the molecules generally adopt puckered, nonplanar conformations. Cyclohexane, for instance, has a puckered shape like a lounge chair rather than a flat shape. Why?

We’ll see in the next chapter that there are two isomeric substances, both named 1,2-dimethylcyclohexane. Explain.

Consider 2-methylbutane (isopentane) sighting along C-2, C-3 bond:

1. Draw a Newman Projection of the most stable conformer.
2. Draw a Newman Projection of the most stable conformer.
3. If a ${\mathbf{CH}}_{\mathbf{3}}\mathbf{-}{\mathbf{CH}}_{\mathbf{3}}$ eclipsing interaction costs 11kJ/mol (2.5 kcal/mol) and a  ${\mathbf{CH}}_{\mathbf{3}}\mathbf{-}{\mathbf{CH}}_{\mathbf{3}}$ gauche interaction costs 3.8kJ/mol (0.9 kcal/mol), make a quantitative plot of energy versus rotation about the C-2 C-3 bond.

Draw a Newman projection along the C2-C3 bond of the following conformation of 2-butanol.

In each of the following sets, which structures represent the same compound and which represent different compounds?

(c)  

In each of the following sets, which structures represent the same compound and which represent different compounds?

(b)  

In each of the following sets, which structures represent the same compound and which represent different compounds?

(a)