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26sec3

  1. 1. 26.3 Carbonyl Compounds
  2. 2. Aldehydes and Ketones <ul><li>Review : </li></ul><ul><ul><li>alcohol has an oxygen bonded to a carbon group and a hydrogen </li></ul></ul><ul><ul><li>ether has an oxygen bonded to two carbon groups </li></ul></ul><ul><li>An oxygen can also be bonded to a single carbon by a double bond </li></ul>
  3. 3. Aldehydes and Ketones <ul><li>The C=O group is called the “carbonyl group” </li></ul><ul><ul><li>it is the functional group in both aldehydes and ketones </li></ul></ul><ul><li>Aldehydes - carbonyl group always joined to at least one hydrogen (meaning it is always on the end !) </li></ul>
  4. 4. Aldehydes and Ketones <ul><li>Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end) </li></ul><ul><li>Structures - middle of page 785 </li></ul>
  5. 5. Aldehydes and Ketones <ul><li>Naming? </li></ul><ul><ul><li>Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al , such as methan al , ethan al , etc. </li></ul></ul><ul><ul><li>Ketones: longest chain w/carbonyl, then new ending of -one ; number it? </li></ul></ul><ul><li>propan one , 2-pentan one , 3-pentan one </li></ul>
  6. 6. Aldehydes and Ketones <ul><li>Table 26.4, page 786 examples </li></ul><ul><li>Neither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcohols </li></ul><ul><li>wide variety have been isolated from plants and animals; possible fragrant odor or taste; many common names </li></ul>
  7. 7. Aldehydes and Ketones <ul><li>Benzaldehyde </li></ul><ul><li>Cinnamaldehyde </li></ul><ul><li>Vanillin </li></ul><ul><li>Methanal (the common name is: formaldehyde) </li></ul><ul><ul><li>40% in water is formalin, a preservative </li></ul></ul>
  8. 8. Aldehydes and Ketones <ul><li>Propanone (common: acetone) is a good solvent; miscible with water in all proportions </li></ul><ul><li>why is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & nonpolar) </li></ul>
  9. 9. The Carboxylic Acids… <ul><li>Also have a carbonyl group (C=O), but is also attached to a hydroxyl group (-OH) = “carboxyl” group </li></ul><ul><li>general formula: R-COOH </li></ul><ul><ul><li>weak acids (ionize slightly) </li></ul></ul><ul><li>Named by replacing -e with -oic and followed by the word acid </li></ul><ul><li>methan oic acid; ethan oic acid </li></ul>
  10. 10. Carboxylic Acids <ul><li>Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin </li></ul><ul><ul><li>acetic acid (ethanoic acid) from acetum, meaning vinegar </li></ul></ul><ul><ul><li>many that were isolated from fats are called fatty acids </li></ul></ul><ul><li>Table 26.6 page 789 </li></ul>
  11. 11. The Esters… <ul><li>General formula: RCOOR </li></ul><ul><li>Derivatives of the carboxylic acids, in which the -OH from the carboxyl group is replaced by an -OR from an alcohol: </li></ul><ul><ul><li>carboxylic acid + alcohol  ester + water </li></ul></ul><ul><li>many esters have pleasant, fruity odors- banana, pineapple, perfumes </li></ul>
  12. 12. Esters <ul><li>Although polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!) </li></ul><ul><ul><li>thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came from </li></ul></ul>
  13. 13. Esters <ul><li>Can be prepared from a carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents) </li></ul><ul><li>Note equation on bottom p. 790 </li></ul>
  14. 14. Esters <ul><li>Naming? It has 2 words: </li></ul><ul><ul><li>1st: alkyl attached to single bonded oxygen from alcohol </li></ul></ul><ul><ul><li>2nd: take the acid name, remove the -ic acid , add -ate </li></ul></ul><ul><li>example on top of page 743 </li></ul>
  15. 15. Oxidation- Reduction Reactions <ul><li>All of the previous clases of organic compounds are related by oxidation and reduction reactions </li></ul><ul><li>What is oxidation-reduction? </li></ul><ul><ul><li>Oxidation: the gain of oxygen, loss of hydrogen, or loss of e -1 </li></ul></ul><ul><ul><li>Reduction: the loss of oxygen, gain of hydrogen, or gain of e -1 </li></ul></ul>
  16. 16. Oxidation- Reduction Reactions <ul><li>Oxidation and reduction reactions (sometimes called redox) are coupled- one does not occur without the other </li></ul><ul><li>The number of Oxygen and Hydrogen attached to Carbon indicates the degree of oxidation </li></ul>
  17. 17. Oxidation- Reduction Reactions <ul><li>The fewer the # of H on a C-C bond, the more oxidized the bond </li></ul><ul><ul><li>Thus, a triple bond is more oxidized than a double bond and a single bond </li></ul></ul><ul><li>An alkane is oxidized (loss of H) to an alkene, and then to an alkyne </li></ul>
  18. 18. Oxidation- Reduction Reactions <ul><li>Loss of hydrogen is called a dehydrogenation reaction </li></ul><ul><ul><li>may require strong heating and a catalyst </li></ul></ul><ul><li>Note equations at the top on page 791 </li></ul>
  19. 19. Oxidation- Reduction Reactions <ul><li>Methane can be oxidized in steps to carbon dioxide (top p. 792): </li></ul><ul><ul><li>methane  methanol  methanal  methanoic acid  CO 2 </li></ul></ul><ul><li>the more reduced (more H) a carbon compound, the more energy it can release upon oxidation </li></ul>
  20. 20. Oxidation- Reduction Reactions <ul><li>Alcohols can also be oxidized into other products </li></ul><ul><li>“ Dr. Al K. Hall  Mr. Al D. Hyde” </li></ul><ul><li>Equations middle of page 792 </li></ul><ul><li>Preparing aldehydes from a primary alcohol is a problem, because they are then easily oxidized to carboxylic acids </li></ul>
  21. 21. Oxidation- Reduction Reactions <ul><li>Benedict’s test and Fehling’s test are commonly used for aldehyde detection – Figure 26.18 p. 793 </li></ul>
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