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12.E: Exercises

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    357335
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    12.4:  Branched Alkanes

    1. Explain why these two molecules are not isomers:

    CNX_Chem_20_01_notiso2_img.jpg

    Answer

    They are the same compound because each is a saturated hydrocarbon containing an unbranched chain of six carbon atoms.

     

    1. Explain why these two molecules are not isomers:

      CNX_Chem_20_01_notiso1_img.jpg

    Answer

    The molecule on the left has a molecular formula of C6H12 while the one on the right has a molecular formula of C6H14. Since they have different numbers of hydrogens, they cannot be isomers.

     

    1. Write the chemical formula and three different Lewis structures for a five-carbon alkane.
    Answer

    C5H12pentane Lewis structure.JPG2-methylbutane Lewis structure.JPG2,2-dimethylpropane Lewis structure.JPG

     

    1. What are the IUPAC names of the alkanes drawn in Exercise 3?
    Answer

    pentane; 2-methylbutane; 2,2-dimethylpropane

     

    1. In the gasoline industry, what is called isooctane is actually 2,2,4-trimethylpentane. Draw the condensed structure of isooctane.
    Answer

    isooctane condensed structure.JPG

     

    1. Isooctane (see Exercise 5) is an isomer of what straight-chain alkane?
    Answer

    octane

     

    1. Name the other three alkane isomers that contain a five-carbon chain with three methyl substituents.
    Answer

    2,2,3-trimethylpentane; 2,3,4-trimethylpentane; 2,3,3-trimethylpentane

     

    1. Draw the Lewis structure and line structure for each of the following hydrocarbons:
      1. hexane
      2. 3-methylpentane
      3. heptane
      4. 3-ethylhexane
    Answer
    1. hexane Lewis structure.JPGhexane line structure.JPG
    2. 3-methylpentane Lewis structure.JPG3-methylpentane line structure.JPG
    3. heptane Lewis structure.JPGheptane line structure.JPG
    4. 3-ethylhexane Lewis structure.JPG3-ethylhexane line structure.JPG

     

    1. Give the complete IUPAC name for each of the following compounds:
      1. CH3CH2CH2CH3
      2. 2-methylpropane condensed structure.JPG
      3. 2-methylbutane condensed structure.JPG
      4. CH3CH2CH3
      5. 3-methylpentane condensed structure.JPG
    Answer
    1. butane
    2. 2-methylpropane
    3. 2-methylbutane
    4. propane
    5. 3-methylpentane

     

    1. Butane is used as a fuel in disposable lighters. Write the Lewis structure for each isomer of butane.
    Answer

    butane Lewis structure.JPG2-methylpropane Lewis structure.JPG

     

    1. Draw line structures of and name the five structural isomers of hexane.
    Answer

    hexane, hexane line structure.JPG

    2-methylpentane, 2-methylpentane line structure.JPG 

    3-methylpentane, 3-methylpentane line structure.JPG 

    2,3-dimethylbutane, 2,3-dimethylbutane line structure.JPG 

    2,2-dimethylbutane, 2,2-dimethylbutane line structure.JPG

     

    12.5:  Alkenes and Alkynes

    1. Draw and name all possible normal (that is, straight-chain) isomers of heptyne.
    Answer

    1-heptyne, 1-heptyne condensed structure.JPG 

    2-heptyne, 2-heptyne condensed structure.JPG 

    3-heptyne, 3-heptyne condensed structure.JPG

     

    1. Write the chemical formula and a Lewis structure of the following, each of which contains five carbon atoms:
      1. an alkene
      2. an alkyne
    Answer
    1. C5H10trans-2-pentene Lewis structure.JPG
    2. C5H82-pentyne Lewis structure.JPG

     

    1. Explain why unbranched alkenes can form geometric isomers while unbranched alkanes cannot. 
    Answer

    It is very difficult to rotate round a carbon-carbon double bond in an alkene so the location of the groups coming off of it is fixed. There is free rotation about a carbon-carbon single bond in an alkane so the groups coming off of the bond occupy all positions.

     

    1. Write the chemical formula, condensed formula, and Lewis structure for each of the following hydrocarbons:
      1. cis-3-hexene
      2. 1-pentene
      3. 3-hexyne
      4. 2-pentyne
      5. trans-3-heptene
      6. 1-hexene
      7. 2-heptyne
    Answer
    1. C6H12cis-3-hexene condensed structure.JPGcis-3-hexene Lewis structure.JPG
    2. C5H101-pentene condensed structure.JPG1-pentene Lewis structure.JPG
    3. C6H103-hexyne condensed structure.JPG3-hexyne Lewis structure.JPG
    4. C5H82-pentyne condensed structure.JPG2-pentyne Lewis structure.JPG
    5. C7H14;trans-3-heptene condensed structure.JPGtrans-3-heptene Lewis structure.JPG
    6. C6H12;1-hexene condensed structure.JPG1-hexene Lewis structure.JPG
    7. C7H122-hexyne condensed structure.JPG2-heptyne Lewis structure.JPG

     

    1. Give the complete IUPAC name for each of the following compounds:
      1. 1-butyne condensed structure.JPG
      2. CH3CH2CH2CH=CH2
      3. 1-octyne condensed structure.JPG
      4. trans-2-pentene line structure.JPG
      5. clipboard_edab3d0ab002d922456ac75fbb04e2d60.png
    Answer
    1. 1-butyne
    2. 1-pentene
    3. 1-octyne
    4. trans-2-pentene
    5. 2-pentyne

     

    1. Write Lewis structures for the cis–trans isomers of CH3CH=CHCH3.
    Answer

    cis:  cis-2-butene Lewis structure.JPG

    trans:  trans-2-butene Lewis structure.JPG

     

    1. Write Lewis structures and IUPAC names for the alkyne isomers of C4H6.
    Answer

    1-butyne:  1-butyne Lewis structure.JPG

    2-butyne:  2-butyne Lewis structure.JPG

     

    12.6:  Oxygen-Containing Organic Compounds

    1. Write the condensed structures of both isomers with the formula C2H6O. Label the functional group of each isomer.
    Answer

    CH3CH2OH, alcohol group; CH3OCH3, ether

     

    1. Write the condensed structures of all isomers with the formula C2H6O2. Label the functional group (or groups) of each isomer.
    Answer

    HOCH2CH2OH, two alcohol groups; CH3OCH2OH, ether and alcohol groups

     

    12.7:  Alcohols, Aldehydes, Carboxylic Acids, and Ketones

    1. Draw the line structures of all the possible isomers of butanol. Include branched isomers.
    Answer

    1-butanol line structure.JPG2-butanol line structure.JPG2-methyl-1-propanol line structure.JPG2-methyl-2-propanol line structure.JPG

     

    1. Why do the compounds hexane, hexanol, and hexene have such similar names?
    Answer

    They all have six carbon chains.

     

    1. Write condensed formulas and provide IUPAC names for the following compounds:
      1. ethyl alcohol (in beverages)
      2. methyl alcohol (used as a solvent, for example, in shellac)
    Answer

    ethanol; ethanol condensed structure.JPG

    methanol; methanol condensed structure.JPG

     

    1. Give the complete IUPAC name for each of the following compounds:
      1. 2-pentanone condensed structure.JPG
      2. butanal condensed structure.JPG
      3. 3-hexanol condensed structure.JPG
      4. pentanoic acid condensed structure.JPG
    Answer
    1. 2-pentanone
    2. butanal
    3. 3-hexanol
    4. pentanoic acid

     

    1. Explain why it is not possible to prepare a ketone that contains only two carbon atoms.
    Answer

    A ketone contains a group bonded to two additional carbon atoms; thus, a minimum of three carbon atoms are needed.

     

    1. Fatty acids are carboxylic acids that have long hydrocarbon chains attached to a carboxylate group. How does a saturated fatty acid differ from an unsaturated fatty acid? How are they similar?
    Answer

    Since they are both carboxylic acids, they each contain the –COOH functional group and its characteristics. The difference is the hydrocarbon chain in a saturated fatty acid contains no double or triple bonds, whereas the hydrocarbon chain in an unsaturated fatty acid contains one or more multiple bonds.

     

    1. Order the following molecules from least to most oxidized, based on the marked carbon atom:

    CNX_Chem_20_03_OxiOrder_img.jpg

    Answer

    Most oxidized is c; intermediate is a; least oxidized is b.

     

    1. Predict the products of oxidizing the molecules shown in this problem. In each case, identify the product that will result from the minimal increase in oxidation state for the highlighted carbon atom:
      1. propanal oxidation.JPG
      2. 1-propanol oxidation.JPG
      3. 2-butanol oxidation.JPG
    Answer
    1. propanal oxidation product.JPG
    2. 1-propanol oxidation product.JPG
    3. 2-butanol oxidation product.JPG

     

    1. Predict the products of reducing the following molecules. In each case, identify the product that will result from the minimal decrease in oxidation state for the highlighted carbon atom:
      1. ethanal reduction.JPG
      2. acetone reduction.JPG
      3. acetic acid reduction.JPG
    Answer
    1. ethanal reduction product.JPG
    2. acetone reduction product.JPG
    3. acetic acid reduction product.JPG

     

    1. Alcohols A, B, and C all have the composition C4H10O. Molecules of alcohol A contain a branched carbon chain and can be oxidized to an aldehyde; molecules of alcohol B contain a linear carbon chain and can be oxidized to a ketone; and molecules of alcohol C can be oxidized to neither an aldehyde nor a ketone. Write the Lewis structures of these molecules.
    Answer

    CNX_Chem_20_03_alcoholABC_img.jpg

     

    12.8:  Esters

    1. The foul odor of rancid butter is caused by butanoic acid, CH3CH2CH2CO2H, commonly known as butyric acid.
      1. Draw the Lewis structure of butyric acid.
      2. The esters formed from butyric acid are pleasant-smelling compounds found in fruits and used in perfumes. Draw the Lewis structure for the ester formed from the reaction of butyric acid with 1-propanol.
    Answer
    1. butanoic acid Lewis structure.JPG
    2. propyl butanoate Lewis structure.JPG

     

    1. Write balanced equations for each of the following reactions using condensed formulas:
      1. ethanol reacts with propanoic acid
      2. 1-butanol reacts with acetic acid (ethanoic acid)
    Answer
    1. ethanol with propanoic acid.JPG
    2. 1-butanol with acetic acid.JPG

     

    12.9:  Ethers

    1. Draw the condensed structure of diethyl ether, once used as an anesthetic.
    Answer

    CH3CH2OCH2CH3

     

    1. Draw the condensed formulas for each of the following compounds:
      1. dipropyl ether
      2. ethyl methyl ether
    Answer
    1. CH3CH2CH2OCH2CH2CH3
    2. CH3CH2OCH3

     

    1. Give the common name for each of the following compounds:
      1. CNX_Chem_20_02_Exercise4a_img.jpg
      2. CNX_Chem_20_02_Exercise4b_img.jpg
      3. CNX_Chem_20_02_Exercise4c_img.jpg
    Answer
    1. butyl ethyl ether
    2. ethyl propyl ether
    3. methyl propyl ether

     

    Additional Exercises

    1. Give the IUPAC name for each of the following molecules.
      1. 4-ethyl-3-methylheptane.JPG
      2. trans-3-hexene.JPG
      3. 2,4-dimethylhexene.JPG
      4. 3-hexanone.JPG
      5. heptanoic acid.JPG
    Answer
    1. 4-ethyl-3-methylheptane
    2. trans-3-hexene
    3. 2,4-dimethylhexane
    4. 3-hexanone
    5. heptanoic acid

     

    1. Write a condensed structural formula for each of the following molecules.
      1. propene
      2. 1-butanol
      3. ethyl propyl ether
      4. cis-2-heptene
      5. 2,2,3-trimethylhexane
      6. methanal (commonly known as formaldehyde)
    Answer
    1. CH2=CHCH3
    2. CH3CH2CH2CH2OH
    3. CH3CH2OCH2CH2CH3
    4. cis-2-heptene condensed structure.JPG
    5. 2,2,3-trimethylhexane condensed structure.JPG
    6. methanal structure.JPG

     

    1. Write a condensed structural formula for each of the following molecules.
      1. 2-propanol
      2. acetone (2-propanone)
      3. dimethyl ether
      4. acetic acid (ethanoic acid)
      5. 1-hexene
    Answer
    1. 2-propanol condensed structure.JPG
    2. acetone condensed structure.JPG
    3. CH3OCH3
    4. acetic acid condensed structure.JPG
    5. CH2=CHCH2CH2CH2CH3

     

    Contributions & Attributions


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