Chapter 21

A confused student was doing an isomer problem and listed the following six names as different structural isomers of \(\mathbf{C}_{7} \mathbf{H}_{16}.\) a. \(1-\) sec-butylpropane d. 1 -ethyl- 1 -methylbutane b. 4 -methylhexane e. 3 -methylhexane c. 2 -ethylpentane f. 4 -ethylpentane How many different structural isomers are actually present in these six names?

For the following formulas, what types of isomerism could be exhibited? For each formula, give an example that illustrates the specific type of isomerism. The types of isomerism are structural, geometric, and optical. a. \(C_{6} H_{12}\) b. \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O} \quad\) c. \(\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Br}_{2}\)

What is wrong with the following names? Give the correct name for each compound. a. 2 -ethylpropane b. 5 -iodo- 5,6 -dimethylhexane c. cis-4-methyl-3-pentene d. 2 -bromo- 3 -butanol

The following organic compounds cannot exist. Why? a. 2 -chloro-2-butyne b. 2 -methyl-2-propanone c. 1,1 -dimethylbenzene d. 2 -pentanal e. 3 -hexanoic acid f. 5,5 -dibromo- 1 -cyclobutanol

If you had a group of hydrocarbons, what structural features would you look at to rank the hydrocarbons in order of increasing boiling point?

A polypeptide is also called a polyamide. Nylon is also an example of a polyamide. What is a polyamide? Consider a polyhydrocarbon, a polyester, and a polyamide. Assuming average chain lengths are equal, which polymer would you expect to make the strongest fibers and which polymer would you expect to make the weakest fibers? Explain.

Give an example reaction that would yield the following products. Name the organic reactant and product in each reaction. a. alkane b. monohalogenated alkane c. dihalogenated alkane d. tetrahalogenated alkane e. monohalogenated benzene f. alkene

What is polystyrene? The following processes result in a stronger polystyrene polymer. Explain why in each case. a. addition of catalyst to form syndiotactic polystyrene b. addition of 1,3 -butadiene and sulfur c. producing long chains of polystyrene d. addition of a catalyst to make linear polystyrene

Answer the following questions regarding the formation of polymers. a. What structural features must be present in a monomer in order to form a homopolymer polyester? b. What structural features must be present in the monomers in order to form a copolymer polyamide? (Hint: Nylon is an example of a polyamide. When the monomers link together to form nylon, an amide functional group results from each linkage.) c. What structural features must be present in a monomer that can form both an addition polymer and a condensation polymer?

Three important classes of biologically important natural polymers are discussed. What are the three classes, what are the monomers used to form the polymers, and why are they biologically important?

Draw the five structural isomers of hexane \(\left(\mathrm{C}_{6} \mathrm{H}_{14}\right).\)

Draw a structural formula for each of the following compounds. a. 2 -methylpropane b. 2 -methylbutane c. 2 -methylpentane d. 2 -methylhexane

Draw a structural formula for each of the following compounds. a. \(2,2-\) dimethylheptane b. 2,3 -dimethylheptane c. \(3,3-\) dimethylheptane d. \(2,4-\) dimethylheptane

Draw the structural formula for each of the following. a. 3 -isobutylhexane b. 2,2,4 -trimethylpentane, also called isooctane. This substance is the reference (100 level) for octane ratings. c. 2 -tert-butylpentane d. The names given in parts a and c are incorrect. Give the correct names for these hydrocarbons.

Draw the structure for 4-ethyl-2,3-diisopropylpentane. This name is incorrect. Give the correct systematic name.

Give two examples of saturated hydrocarbons. How many other atoms are bonded to each carbon in a saturated hydrocarbon?

Draw the structures for two examples of unsaturated hydrocarbons. What structural feature makes a hydrocarbon unsaturated?

Give the structure for each of the following. a. 3 -hexene b. \(2,4-\) heptadiene c. 2 -methyl- 3 -octene

Give the structure for each of the following. a. 4 -methyl- 1 -pentyne b. 2,3,3 -trimethyl- 1 -hexene c. 3 -ethyl- 4 -decene

Give the structure of each of the following aromatic hydrocarbons. a. \(o\) -ethyltoluene b. \(p\) -di-tert-butylbenzene c. \(m\) -diethylbenzene d. \(1-\) phenyl- 2 -butene

Cumene is the starting material for the industrial production of acetone and phenol. The structure of cumene is Give the systematic name for cumene.

There is only one compound that is named 1,2 -dichloroethane, but there are two distinct compounds that can be named 1,2-dichloroethene. Why?

Draw all the structural isomers of \(\mathrm{C}_{5} \mathrm{H}_{10}\). Ignore any cyclic isomers.

Draw all the structural and geometrical (cis-trans) isomers of bromochloropropene.

Draw all structural and geometrical (cis-trans) isomers of \(\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{F}\). Ignore any cyclic isomers.

Cis-trans isomerism is also possible in molecules with rings. Draw the cis and trans isomers of 1,2 -dimethylcyclohexane. In Exercise \(41,\) you drew all of the noncyclic structural and geometric isomers of \(\mathbf{C}_{4} \mathrm{H}_{7} \mathrm{F}\). Now draw the cyclic structural and geometric isomers of \(\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{F}\).

Draw the following. a. cis-2 -hexene b. trans- 2 -butene c. cis-2,3 -dichloro-2-pentene

If one hydrogen in a hydrocarbon is replaced by a halogen atom, the number of isomers that exist for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon. Thus there is only one form of chloroethane (all hydrogens in ethane are equivalent), but there are two isomers of propane that arise from the substitution of a methyl hydrogen or a methylene hydrogen. How many isomers can be obtained when one hydrogen in each of the compounds named below is replaced by a chlorine atom? a. \(n\) -pentane c. 2,4 -dimethylpentane b. 2 -methylbutane d. methylcyclobutane

There are three isomers of dichlorobenzene, one of which has now replaced naphthalene as the main constituent of mothballs. a. Identify the ortho, the meta, and the para isomers of dichlorobenzene. b. Predict the number of isomers for trichlorobenzene. c. It turns out that the presence of one chlorine atom on a benzene ring will cause the next substituent to add ortho or para to the first chlorine atom on the benzene ring. What does this tell you about the synthesis of \(m\) -dichlorobenzene? d. Which of the isomers of trichlorobenzene will be the hardest to prepare?

Mimosine is a natural product found in large quantities in the seeds and foliage of some legume plants and has been shown to cause inhibition of hair growth and hair loss in mice. a. What functional groups are present in mimosine? b. Give the hybridization of the eight carbon atoms in mimosine. c. How many \(\sigma\) and \(\pi\) bonds are found in mimosine?

Draw structural formulas for each of the following alcohols. Indicate whether the alcohol is primary, secondary, or tertiary. a. \(1-\) butanol c. 2 -methyl- 1 -butanol b. 2-butanol d. 2 -methyl- 2 -butanol

Name all the alcohols that have the formula \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\). How many ethers have the formula \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O} ?\)

Name all the aldehydes and ketones that have the formula \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}\)

Draw the structural formula for each of the following. a. formaldehyde (methanal) b. 4 -heptanone c. 3 -chlorobutanal d. \(5,5-\) dimethyl- 2 -hexanone

Draw a structural formula for each of the following. a. 3 -methylpentanoic acid b. ethyl methanoate c. methyl benzoate d. 3 -chloro- 2,4 -dimethylhexanoic acid

Draw the isomer(s) specified. There may be more than one possible isomer for each part. a. a cyclic compound that is an isomer of trans-2-butene b. an ester that is an isomer of propanoic acid c. a ketone that is an isomer of butanal d. a secondary amine that is an isomer of butylamine e. a tertiary amine that is an isomer of butylamine f. an ether that is an isomer of 2 -methyl-2-propanol g. a secondary alcohol that is an isomer of 2-methyl-2-propanol

Reagents such as HCI, HBr, and HOH (H_O) can add across carbon-carbon double and triple bonds, with H forming a bond to one of the carbon atoms in the multiple bond and \(\mathrm{Cl}, \mathrm{Br},\) or OH forming a bond to the other carbon atom in the multiple bond. In some cases, two products are possible. For the major organic product, the addition occurs so that the hydrogen atom in the reagent attaches to the carbon atom in the multiple bond that already has the greater number of hydrogen atoms bonded to it. With this rule in mind, draw the structure of the major product in each of the following reactions. a. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{H}_{2} \mathrm{O} \stackrel{\mathrm{H}^{2}}{\longrightarrow}\) b. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{HBr} \longrightarrow\) c. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{C} \equiv \mathrm{CH}+2 \mathrm{HBr} \longrightarrow\)

When toluene \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{3}\right)\) reacts with chlorine gas in the presence of iron(III) catalyst, the product is a mixture of the ortho and para isomers of \(\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{ClCH}_{3}\). However, when the reaction is light-catalyzed with no \(\mathrm{Fe}^{3+}\) catalyst present, the product is \(\mathbf{C}_{6} \mathbf{H}_{5} \mathrm{CH}_{2} \mathrm{Cl} .\) Explain.

Why is it preferable to produce chloroethane by the reaction of HCI(g) with ethene than by the reaction of \(\mathrm{Cl}_{2}(g)\) with ethane? (See Exercise 62.)

Using appropriate reactants, alcohols can be oxidized into aldehydes, ketones, and/or carboxylic acids. Primary alcohols can be oxidized into aldehydes, which can then be oxidized into carboxylic acids. Secondary alcohols can be oxidized into ketones, while tertiary alcohols do not undergo this type of oxidation. Give the structure of the product(s) resulting from the oxidation of each of the following alcohols. a. 3 -methyl-l-butanol b. 3 -methyl- 2 -butanol c. 2 -methyl-2-butanol

Oxidation of an aldehyde yields a carboxylic acid: Draw the structures for the products of the following oxidation reactions. a. propanal \(\stackrel{\text { [ox] }}{\rightarrow}\) b. 2,3 -dimethylpentanal \(\stackrel{\text { [ox] }}{\longrightarrow}\) c. 3 -ethylbenzaldehyde \(\stackrel{\text { [ox] }}{\longrightarrow}\)

How would you synthesize each of the following? a. 1,2-dibromopropane from propene b. acetone (2-propanone) from an alcohol c. tert-butyl alcohol ( 2 -methyl-2-propanol) from an alkene (See Exercise 62.) d. propanoic acid from an alcohol

What tests could you perform to distinguish between the following pairs of compounds? a. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}, \quad \mathrm{CH}_{2}=\mathrm{CHCH}_{2} \mathrm{CH}_{3}\) d. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}, \quad \mathrm{CH}_{3} \mathrm{OCH}_{3}\)

How would you synthesize the following esters? a. \(n\) -octylacetate

Complete the following reactions. a. \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}+\mathrm{CH}_{3} \mathrm{OH} \rightarrow\) b. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{HCOOH} \rightarrow\)

Kel-F is a polymer with the structure What is the monomer for Kel-F?

Isoprene is the repeating unit in natural rubber. The structure of isoprene is a. Give a systematic name for isoprene. b. When isoprene is polymerized, two polymers of the form are possible. In natural rubber, the cis configuration is found. The polymer with the trans configuration about the double bond is called gutta percha and was once used in the manufacture of golf balls. Draw the structure of natural rubber and gutta percha showing three repeating units and the configuration about the carbon-carbon double bonds.

The Amoco Chemical Company has successfully raced a car with a plastic engine. Many of the engine parts, including piston skirts, connecting rods, and valve- train components, were made of a polymer called Torlon: What monomers are used to make this polymer?

Polystyrene can be made more rigid by copolymerizing styrene with divinylbenzene: How does the divinylbenzene make the copolymer more rigid?

Polyesters containing double bonds are often crosslinked by reacting the polymer with styrene. a. Draw the structure of the copolymer of \(\mathrm{HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{OH} \quad\) and \(\quad \mathrm{HO}_{2} \mathrm{C}-\mathrm{CH}=\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H}\) b. Draw the structure of the crosslinked polymer (after the polyester has been reacted with styrene).