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ALDEHYDES AND KETONES

ALDEHYDES AND KETONES. SUBMITTED TO: MRS. SANGITA NORIA. SUBMITTED BY: 8769,8773,8774,8775,8776,8777,8780,. THE CARBONYL GROUP. • The carbonyl group (C=O) is found in aldehydes, ketones, and many other organic functional groups. • The carbon and oxygen in the carbonyl group are

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ALDEHYDES AND KETONES

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  1. ALDEHYDES AND KETONES SUBMITTED TO: MRS. SANGITA NORIA SUBMITTED BY: 8769,8773,8774,8775,8776,8777,8780,

  2. THE CARBONYL GROUP • The carbonyl group (C=O) is found in aldehydes, ketones, and many other organic functional groups. • The carbon and oxygen in the carbonyl group are sp2-hybridized, with bond angles of 120°.

  3. • In ketones, two carbon groups are attached to the carbonyl carbon, while in aldehydes at least one hydrogen is attached to the carbon

  4. NOMENCLATURE ALDEHYDES Aldehydes are named by replacing the terminal -e of the corresponding alkane name with –al The parent chain must contain the CHO group The CHO carbon is numbered possible minimum number.

  5. ALDEHYDES • IUPAC • LONGEST CHAIN WITH ALDEHYDE • DROP “e” AND ADD “-al” • ALDEYHYDE TAKES PRECEDENCE OVER ALL OTHER GROUPS SO FAR. • EXAMPLES

  6. Naming Ketones Replace the terminal -e of the alkane name with –one Parent chain is the longest one that contains the ketone group Numbering begins at the end nearer the carbonyl carbon

  7. Ketones with Common Names IUPAC retains well-used but unsystematic names for a few ketones

  8. FORMATION OF ALDEHYDES Oxidation of Primary Alcohols The aldehyde can be oxidized in a second step [O] represent an oxidation

  9. OXIDATION OF SECONDARY ALCOHOLS

  10. OXIDATION OF TERTIARY ALCOHOLS

  11. OXIDATION OF PRIMARY ALCOHOLS TO ALDEHYDES • Requires less vigorous oxidation conditions. • We can try to remove the aldehyde from the reaction medium as quickly as it is formed • Generally, the aldehyde has a lower boiling point than either the corresponding alcohol or carboxylic acid • We can also try to find a milder oxidizing agent.

  12. DEHYDROGENATION OVER COPPER • This reaction is generally done by passing the vapors of the alcohol through a tube furnace in a stream of inert carrier gas. • This is not a practical laboratory method -- it is better suited to industrial processes. • The reaction stops at the aldehyde stage -- no more removal of hydrogen can take place.

  13. Oxidation of Primary Alcohols with K2Cr2O7 • This reaction can also be done using CrO3 (chromic oxide) in sulfuric acid. • The aldehyde is distilled away from the reaction vessel as quickly as it is formed. If the aldehyde is not removed, it will suffer a second oxidation, and the product will be the carboxylic acid.

  14. The acidic conditions keep the chromium in the Cr2O72- state. • Potassium dichromate is not as powerful an oxidizing agent as is potassium permanganate • Sodium dichromate can be substituted for potassium dichromate -- it makes no difference. • There is a color change during the reaction. The orange color of the dichromate changes to the green of Cr3+ ion. • This is not the world’s greatest way to prepare an aldehyde!

  15. OXIDATION WITH CHROMIC OXIDE AND PYRIDINE Sarett Oxidation

  16. OXIDATION WITH PYRIDINE CHLOROCHROMATE “PCC” Oxidation

  17. CHANGE OF GEARS: • Aldehydes can be oxidized to carboxylic acids. • This oxidation can take place under very mild oxidizing conditions. • Aldehydes can be oxidized with such weak oxidizing agents as metal cations, especially: • Ag+ Cu2+

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