LECTURE MATERIAL FOR CHAPTER 12 -UNSATURATED HYDROCARBONS.

TO VIEW THE STRUCTURAL FORMULAS OF MANY -IF NOT ALL OF THE FOLLOWING-

USE THE LINK TO CABRILLO LIBRARY OF MOLECULES

YOU WILL NEED TO DOWNLOAD A PLUGIN CALLED CHIME TO VIEW THE MOLECULES.

I RECOMMEND USING THE "OLD VERSION"

REMEMBER YOU DO NOT HAVE TO LOOK AT THESE MOLECULES IF YOU DO NOT HAVE THE TIME.


CABRILLO LIBRARY OF MOLECULES

AND CHECK OUT THE MANY MOLECULES IN THE TABLE OF CONTENTS.

 

 

ALKENES - UNSATURATED MOLECULES WITH DOUBLE BONDS

These are molcules which contain one or more double bonds. The double bonds decrease the number of hydrogen atoms in the compound by two. Each double bond is = to the removal of two [2] hydrogen atoms.

 

THE GENERAL FORMULA FOR ALKENES WITH ONE DOUBLE BOND IS

CNH2N

 

This means that the molecule no longer has the maximum number of hydrogens - that the molecules carbon chain is no longer saturated with hydrogens and is therefore unsaturated.

 

 

The double bond is very reactive and can react with many different kinds of reagents. These reactions are called addition reactions because they add atoms to the formula of the alkene.

 

The simplest alkene is ethene or ethylene. This is the hormone in plants responsible for leaf abscission [dropping] and for the ripening of fruit. It is used to ripen apples out of season. It is also responsible for the wilting of roses.

courtesy the State of Maine

Alkenes and geometrical or cis-trans isomerism are essential to an understanding of the chemistry of vision.

Sample problems :

Be sure to look over the examples above and in your text.

1. What is the general formula for any alkane? For any alkene?




Answer

2. What is the most common reaction type for alkanes [excluding combustion]? What is the most common reaction type for alkenes [excluding combustion]?



Answer

 

 

 

HERE IS A LINK TO A WEB SITE THAT HAS A REVIEW OF FAT-SOLUBLE VITAMINS AND SPECIFICALLY

BETA-CAROTENE AND VITAMIN A.

VITAMIN A & BETA CAROTENE

Here is a web site discussing beta-carotene and cigarette smoking

BETA CAROTENE & SMOKING

 

HERE IS A LINK TO A WEB SITE THAT HAS A REVIEW OF SOME ASPECTS OF ALKENES.

ALKENES

 

 

PHYSICAL PROPERITES

NON-POLAR [ZERO OR VERY SMALL DIPOLE MOMENT]
INSOLUBLE IN POLAR SOLVENTS LIKE WATER

SOLUBLE IN NON-POLAR SOLVENTS LIKE CARBON TETRACHLORIDE

 

Sample problems :

Be sure to look over the examples above and in your text.

3. What is name and molecular formula for the alkene that is the ripening hormone for fruit and also the leaf abscission hormone?


Answer



4. As a general rule, alkenes will be soluble or non-soluble in water?



Answer

 

 

 

NOMENCLATURE OF ALKENES [ PAGE362 ]

HERE IS A LINK TO A WEB SITE THAT HAS A REVIEW OF SOME ASPECTS OF ALKENES.

IUPAC

 

 


Sample problems :

Be sure to look over the examples above and in your text.

5. Give an accepted name for the following compound.

 


Answer

 



6. Give a structural formula for 2-butene.




Answer

 

 


READ ABOVE

 

GEOMETRY OF ALKENES [ PAGE 366 ]

Sample problems :

Be sure to look over the examples above and in your text.

7. Which of the following will have the higher boiling point?

butane or isobutane [2-methylpropane]



Answer

8. Are butane and 2-methylpropane [ isobutane ] positional isomers

or constitutional isomers?



Answer

 

 

 

Sample problems :

Be sure to look over the examples above and in your text.

9. Is the following molecule a cis or a trans isomer?





Answer

10. As a general rule which isomer will have the higher boiling point - the cis or the trans?




Answer

 

 

 

PROPERTIES OF ALKENES [ PAGE 371 ]

 

ALKENE

 

ALKYL DIHALIDES

OR

HALOALKANES
ALKANES
 ALKYL HALIDES ALCOHOLS

 

 

The chart above is a summary of the important reactions for the alkenes. They are all adddition reactions. The pi

electrons of the double bond or unsaturated linkage can be viewed as a sponge that absorbs chemicals rather than water. The molecular weight of the molecule increases just as the weight of the sponge increases.

Below are some more details on these addition reactions.

Sample problems :

Be sure to look over the examples above and in your text.

11. Do alkenes or olefins undergo

a. addition reactions

b. substitution reactions

c. elimination reactions?



Answer

12. The reaction of an alkene with dihydrogen gas and a metal catalyst will yield what class of organic chemical?




Answer

 

 

 

REACTIONS OF ALKENES

 

 

 


 

Sample problems :

Be sure to look over the examples above and in your text.

13. What is the name of the product of the following reaction?





Answer

14. How is the preceding reaction[ Question 13] classified as-

a. an addition [hydration]

b. an elimination [a dehydration ]?




Answer

 

 

 

Sample problems :

Be sure to look over the examples above and in your text.

15. What alkene would be required for the following reaction?




Answer

16. Whose rule describes the addition of water to an unsaturated linkage?



Answer

 

 

 

ADDITION POLYMERS OF ALKENES [ PAGE 375 ]

 

 

 

ALKYNES [ PAGE 379 ]

 

ALKYNES OR ACETYLENES - UNSATURATED MOLECULES WITH TRIPLE BONDS

 

 

 

PHYSICAL PROPERITES OF ACETYLENE DERIVATIVES OR ALKYNES

NON-POLAR [ZERO OR VERY SMALL DIPOLE MOMENT]
INSOLUBLE IN POLAR SOLVENTS LIKE WATER

SOLUBLE IN NON-POLAR SOLVENTS LIKE CARBON TETRACHLORIDE

 

 

REACTIONS

We will not study the reactions of the alkynes in this course [CHEM 146]. but they are mostly addition reactions.

NOMENCLATURE

HERE IS A LINK TO A WEB SITE THAT HAS A REVIEW OF SOME ASPECTS OF ALKYNES.

IUPAC

 

 

 

 

 

 

SOME FURTHER EXAMPLES OF ALKYNE NOMENCLATURE - INCLUDING BOTH THE IUPAC AND RADICAL SYSTEMS

 

AROMATIC COMPOUNDS AND BENZENE[ PAGE 381 ]

AROMATIC HYDROCARBONS - BENZENE AND ITS DERIVATIVES

NOMENCLATURE OF AROMATICS [ PAGE 382 ]

 

 

 

 

 

 

 

 

Essentially, this involves memorization of the names and formulas of certain compounds. After selecting the appropriate parent name one numbers the substituents present by counting around the ring so as to give the lowest numbers posssible.

 

 

 

 

 

 

PROPERTIES AND USES OF AROMATICS [ PAGE 384 ]

 

 

PHYSICAL PROPERITES

NON-POLAR [ZERO OR VERY SMALL DIPOLE MOMENT]
INSOLUBLE IN POLAR SOLVENTS LIKE WATER

SOLUBLE IN NON-POLAR SOLVENTS LIKE CARBON TETRACHLORIDE

 

 


Animation courtesy of Suresh Srinivasan

 

1. Alkanes have the general formula CNH2N+2. They are saturated molecules because they cannot accomodate any more hydrogen atoms due to the tetravalency of carbon.

Alkenes have the general formula CNH2N. They are unsaturated molecules and have a double bond as their characteristic functional group. They can undergo the addition of other molecules like dihydrogen gas.  




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2.  Addition reactions are characteristic of alkenes. Below is shown a typical addition reaction in which propene is convertedinto propane by the addition of dihydrogen gas.

Note the increase in the molecular formula after the reaction is over.



 

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3.  




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 4. Alkenes as well as alkanes will be insoluble in water. As a rule of thumb, like dissolves in like. Polar molecules dissolve in polar molecules and non-polar molecules dissolve in non-polar molecules. Since hydrocarbons are essentially non-polar and water is very polar, they do not mix.

BIRDS OF A FEATHER FLOCK TOGETHER




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5.  

2-methyl-1-propene

isobutene

isobutylene



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6.

THE ANSWER IS C.






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7. Which of the following will have the higher boiling point?

butane

In general the unbranched isomer will have the higher boiling point. This is very important rule when gasoline which is a blend of hydrocarbons is being made.






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8.

butane and 2-methylpropane [ isobutane ] are

constitutional isomers





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9. Is the following molecule is a cis isomer because the two methyl groups shown in red are on the same side of the molecule.

 





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10.As a general rule the cis isomer will have the higher boiling point .





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11.Alkenes or olefins will undergo

a. addition reactions






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12.The reaction of an alkene with dihydrogen gas and a metal catalyst will yield alkanes or saturated hydrocarbons.





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13.The name of the product of the following reaction is ethyl alcohol.

 





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14.How is this reaction classified as an addition [hydration] reaction.

 






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15. Propene or propylene would be required for the following reaction.

 





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16. Markovnikov's rule.





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