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Functional Groups with the C = O Bond

Functional Groups with the C = O Bond. Aldehydes, Ketones, Carboxylic Acids, Esters and Amides. The Carbonyl Group. Functional group where a carbon atom is double-bonded to an oxygen atom Is this functional group likely to result in polar or non-polar molecules?. Aldehydes and Ketones.

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Functional Groups with the C = O Bond

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  1. Functional Groups with the C = O Bond Aldehydes, Ketones, Carboxylic Acids, Esters and Amides

  2. The Carbonyl Group • Functional group where a carbon atom is double-bonded to an oxygen atom • Is this functional group likely to result in polar or non-polar molecules?

  3. Aldehydes and Ketones • Both have a carbonyl functional group • Aldehydes – the carbonyl group attached to an end carbon. • Ketones – the carbonyl group attached to an interior carbon.

  4. Naming an Aldehyde • Name the parent alkane. The carbon of the carbonyl group is position 1. • Replace the “-e” with the suffix –al. • Name side chains using regular IUPAC rules. Note: No position number is needed for the carbonyl group (always #1)

  5. Examples of Naming Aldehydes • Name the following aldehydes: Methanal (formaldehyde) Butanal

  6. Naming Ketones • Name the parent alkane. Main chain must contain carbonyl group. • Replace “-e” with the suffix “-one”. If more than 1 carbonyl, use -dione, -trione, etc. • If more than 4 carbons (main chain) a position number is needed for the carbonyl group. • Name side chains according to IUPAC rules.

  7. Examples for Naming Ketones • Name the following: 3-hexanone 3-propyl-2,6-octadione

  8. Physical Properties • The C=O bond is polar, so aldehydes and ketones are usually polar • H-bonds not possible b/n these molecules, but they can be formed with water • With low molecular masses – very soluble in water • Boiling points

  9. Other characteristics Aldehydes Ketones Sweet smell Used in perfumes Smell of roses is due to ketones Polar solvents Can be solvents for non-polar compounds • Strong, pungent smell • Long chains used in perfume • Polar solvents • Can be solvents for non-polar compounds

  10. Carboxylic Acids • Organic compounds with the functional group, -COOH in a complete structural diagram it looks like, • Naming carboxylic acids • Name the parent alkane. • Replace the “-e” with “–oic acid”. The carbon with the carbonyl group is number 1. • Name and number the branches as usual.

  11. Examples of carboxylic acids • Name the following:

  12. Drawing Carboxylic Acids • Draw the following: • 4-ethyl-2,3-dimethylhexanoic acid • propenoic acid • 3-methylbenzoic acid

  13. Properties of Carboxylic Acids • Polar compounds • Due to hydroxyl (-OH) group, form two H-bonds with each other and water • Low molecular weight compounds are miscible with water • Solubility decreases as size increases • Very high boiling and melting points due to H-bonds

  14. Additional Characteristics of Carboxylic Acids • Often have unpleasant odours (butanoic acid – rancid butter) • In water, the H from the –OH group dissociates, so they behave like acids • This happens because the 2 O atoms can accommodate the free electron (they are very electronegative)

  15. Relative boiling points • Rank in order from highest to lowest

  16. Carboxylic Acid Derivatives • The hydroxyl group is exchanged • Esters • Have the general formula RCOOR’ • Formed by the following dehydration reaction: carboxylic acid + alcohol  ester + water

  17. Parts of an ester • Esters are split into 2 parts • The parent acid, contains the C=O • The alkyl group

  18. Naming Esters • Identify the parent acid. Name the parent acid. • Replace the “–oic acid” part of the name with “-oate”. • Name the alkyl part of the molecule like any other alkyl group. • Put 2 names together. The alkyl group and parent acid remain separate words.

  19. Examples • Name the following: • CH3CH2CH2COOCH2CH3 • CH3CH2CH2CH2CH2CH2COOCH2CH3 • HCOOCH2CH3

  20. Properties of Esters • Polar molecules • No O-H bond, so can’t form H-bond with other esters • Can form H-bonds with water • If molecular weight is low • Soluble in water • Longer than 4 carbons = not soluble • Low boiling points due to lack of H-bonds

  21. Other Properties • Many have pleasant smells and tastes • Used in perfumes and artificial flavours • Taste and smell of many fruits comes from esters

  22. Amides • Combination of a carboxylic acid and an amine. • General formula: R – CO – NR2 • R can be a H atom or an alkyl group

  23. Naming Amides • Name the carboxylic acid part of the molecule (contains C=O). • Drop the “oic acid” with the suffix “-amide”. The C=O carbon is position 1. • Name the alkyl groups attached to the N in alphabetical order. Use the letter “N” to indicate position. If there are identical groups use N,N- • Write the prefix, root and suffix together

  24. Name the following N,N – diethylbutamide N – ethyl – N – methylbutamide

  25. Types of Amides • Primary – only H attached to the N, no alkyl groups • Secondary – 1 alkyl group attached to the N • Tertiary – 2 alkyl groups attached to the N

  26. Physical Properties of Amides • C-N and N-H bonds are polar • Properties are similar to carboxylic acids • Primary amides have 2 N-H bonds, therefore they have even more H-bonding than carboxylic acids...very high boiling points • Amides are soluble in water. This decreases as size increases.

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