005_C1080_Organic-Aldehydes,Ketones_CH14.pptx

ALDEHYDES AND KETONES CHAPTER 4 H. O’BRIEN TUESDAY, SEPTEMBER 19, 2023  ALDEHYDES AND KETONES The carbonyl group: Aldehydes have at least one hydrogen attached to the carbonyl group Ketones have two carbons attached to the carbonyl group.  NA...

ALDEHYDES AND KETONES CHAPTER 4 H. O’BRIEN TUESDAY, SEPTEMBER 19, 2023  ALDEHYDES AND KETONES The carbonyl group: Aldehydes have at least one hydrogen attached to the carbonyl group Ketones have two carbons attached to the carbonyl group.  NAMING ALDEHYDES Find the longest carbon chain that contains the aldehyde group Change ending of the root hydrocarbon name by dropping –e and adding –al Number the longest carbon chain so the C=O group has the lowest number All other branches and groups are named and located using standard IUPAC system 3-bromobutanal 2-ethylbutanal  NAMING KETONES Find the longest chain that contains C=O Using the root alkane name, drop the –e ending and change to – one Number the longest carbon chain so the C=O group has the lowest number Name and number other substituents as before  IMPORTANT ALDEHYDES AND KETONES  Formaldehyde Gas at room temperature Formalin is a 37% aqueous solution Sterilizer Embalming fluid Starting material for plastics such as Formica and Bakelite  IMPORTANT ALDEHYDES AND KETONES  Acetone (propanone) Important organic solvent Used in such things as nail polish remover Miscible with water  IMPORTANT ALDEHYDES AND KETONES  Progesterone and Testosterone (female and male sex hormones) are ketones  Some aldehydes and ketones are very fragrant and are used in flavorings Vanillin (vanilla) Cinnamaldehyde (cinnamon) Citral (citrus flavoring) Camphor (medicinal odor) PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES The carbonyl group is moderately polar, but it doesn’t have any hydrogen atoms bonded to the oxygen atom, so it cannot hydrogen bond between molecules Because of the polarity of the C=O group, these groups can interact, but the attraction is not as strong as hydrogen bonding This makes the boiling point of aldehydes and ketones higher than alkanes, but lower than PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES  PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES The C=O group can hydrogen bond with water molecules because the oxygen atom in the carbonyl group has a partial negative charge that attracts the partial positive charge of a hydrogen atom in the water molecule This makes low molecular weight aldehydes and ketones water  REACTIONS OF ALDEHYDES AND KETONES  Oxidation > Recall the oxidation of alcohols produces aldehydes and ketones  REACTIONS OF ALDEHYDES AND KETONES > The difference in reactivity toward oxidation is the chief reason why aldehydes and ketones are classified in separated families  REACTIONS OF ALDEHYDES AND KETONES  Hydrogenation > Aldehydes and ketones are reduced to alcohols by the addition of H2 in the presence of catalysts  REACTIONS OF ALDEHYDES AND KETONES Ex.  REACTIONS OF ALDEHYDES AND KETONES  The addition of alcohols to aldehydes produces an unstable hemiacetal intermediate REACTIONS OF ALDEHYDES AND KETONES  General Formulas Hemiacetals Acetals REACTIONS OF ALDEHYDES AND KETONES  REACTIONS OF ALDEHYDES AND KETONES  The addition of alcohol to ketones produces an unstable hemiketal intermediate REACTIONS OF ALDEHYDES AND KETONES  General formulas Hemiketal Ketal  Cyclic hemiacetals and hemiketals are more stable than open chains and are important in carbohydrate chemistry  Acetals and ketals are stable but may be converted back to aldehydes and ketones through acid catalyzed hydrolysis Hydrolysis is the breakage of a bond by reaction with water Acetal Hydrolysis  Ketal Hydrolysis: Specific Example REACTIONS OF ALDEHYDES AND KETONES  Next Topic > Carboxylic Acids/Esters