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Cycloalkanes, Isomers, and Organic Compounds

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I) What causes cycloalkanes to have two less hydrogen atoms than similar alkanes that are open chain ones?
i) What is the three dimensional structure of methane? Why?
ii) Name an isomer of pentane (that is not cyclic), and write down its structure.
iii) Name the compounds that are organic:
(1) KMnO4
(2) CH3OH
(3) C6H6
(4) PdCl2
(5) CH3CO2H
iv) Are any of these substances organic? Why?
i) Name one structural and one chemical difference between acetylene and ethylene. Give reasons.
ii) What is the formula of 1, 3-butadiene?
iii) Why is benzene much less reactive than 1, 3, 5-cyclohexatriene?
iv) Why is the benzene molecule represented as "a flat cyclohexane with a ring inside?"
v) Why do cis and trans isomeric compounds exhibit different properties?

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i) What causes cycloalkanes to have two less hydrogen atoms than similar alkanes that are open chain ones?
To form the cycloalkane from the open chain alkane, the two ends of the molecule must bond together. In so doing, two hydrogens are lost in order to make the C-C bond.

i) What is the three dimensional structure of methane? Why?
It's in the shape of a tetrahedron. This occurs in order to maximize the bond angles between each C-H bond and reduce steric hindrance between the hydrogens.

ii) Name an isomer of pentane (that is not cyclic), and write down its structure.
CH3
|
CH3-C-CH2-CH3
|
H
This is 2-methylbutane, an isomer of pentane. Notice that it still has five carbons and is fully saturated, as is ...

Solution Summary

This solution provides answers to questions regarding organic compounds and cycloalkanes.

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Introductory Organic Chemistry: Formulas and Naming

1. Write structural formulas for the following compounds:
a. 2,4-dimethylpentane
b. 3-bromo-1-chlorohexane
c. 1,2-dimethylcyclobutane
d. 2-chloro-1-methylcyclohexane

2. Write expanded formulas for the following compounds, and name them, using the IUPAC system:
a. CH3CH2C(CH3)2CH3
b. CH3CH2Cl
c. CHCl2CHBrCl
d. (CH3)3CF

3. What is the molecular formula for the alkane with 39 carbon atoms? What is the molecular formula for the cycloalkane with 38 carbon atoms?

4. Write the structural formula for all the possible isomers (the number is indicated in parentheses) for each of the following compounds, and name each isomer by the IUPAC system.
a. C4H9Cl (4)
b. C4H8Br2 (9)

5. Draw all possible staggered and eclipsed conformations of 1-bromopropane (looking end-on at the bond between carbon-1 and carbon-2). Underneath each, draw the corresponding "dash-wedge" and "sawhorse" structures. Rank the structures in order of decreasing stability.

6. Draw the formula for the preferred chair conformation of:
a. cis-1,3-dibromocyclohexane
b. trans-1-methyl-2-ethylcyclohexane
c. trans-1-chloro-4-iodocyclohexane

7. Which of the following two isomers in each case will be more stable? Explain your answer by drawing conformational structures for each compound.
a. cis-1,3-dichlorocyclohexane or trans-1,3-dichlorocyclohexane
b. cis-1,2-dibromocyclohexane or trans-1,2-dibromocyclohexane

8. Explain the difference between structural isomerism and conformational isomerism. Give examples.

9. Draw structural formulas for all possible products of the dichlorination of cyclohexane. Include cis-trans isomers.

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