Amides

Page 1: Introduction to Amides

• Amides: A class of compounds where the hydroxyl group of carboxylic acids is replaced by a nitrogen group from primary or secondary amines.

• Example: Tylenol (acetaminophen) is an amide that reduces fever and pain, though it has minimal anti-inflammatory effects.

Page 2: Preparation of Amides

• Amides are derived from carboxylic acids.

• Formation involves replacing the hydroxyl group (-OH) of a carboxylic acid with a nitrogen group from a primary or secondary amine.

Page 3: Process of Amidation

• Amidation Reaction: The synthesis of amides occurs through a reaction called amidation or condensation.

• Chemical Reaction: A carboxylic acid reacts with ammonia or a primary/secondary amine under heat, resulting in the formation of an amide and the release of water.

Page 4: Learning Check 1

• Task: Predict the products of a specific amidation reaction (details not provided).

Page 5: Solution 1

• Task Resolution: Predict the products of amidation (specifics not provided).

Page 6: Naming Amides

• Amides are named by modifying the name of the corresponding carboxylic acid:

  • Drop "oic acid" (IUPAC) or "ic acid" (common) from the name.

  • Add the suffix "amide".

Page 7: Alkyl Groups in Amides

• When alkyl groups are attached to the nitrogen atom in an amide:

  • They are indicated with the prefix N- followed by the alkyl name.

Page 8: IUPAC Naming Steps

• Example Task: Given an amide structure, determine the IUPAC name.

• Steps to Name:

  1. Replace "oic acid" in the carboxylic acid name with "amide".

  2. For alkyl substituents on nitrogen, use the prefix N-.

Page 9: Continued Naming Guidance

• Further steps to name amides include indicating each substituent on the nitrogen with the N- prefix and the corresponding alkyl name.

Page 10: Learning Check 2

• Task: Identify the IUPAC and common names for given amides A and B (specifics not provided).

Page 11: Solution 2

• Example Names:

  • A: ethanamide (IUPAC), acetamide (common).

  • B: N-ethylpropanamide (IUPAC), N-ethylpropionamide (common).

Page 12: Physical Properties of Amides

• Amides largely lack the basic properties of amines.

• At room temperature:

  • Only methanamide is liquid; others are solids.

• Melting Points:

  • Primary amides have the highest due to maximized hydrogen bonding.

  • Secondary amides have lower melting points than primary.

  • Tertiary amides cannot form hydrogen bonds and have the lowest melting points.

Page 13: Melting Points Overview

• Selected Amides and Melting Points:

  • Primary (Propanamide): 80 °C

  • Secondary (N-Methylethanamide): 28 °C

  • Tertiary (N,N-Dimethylmethanamide): -61 °C.

Page 14: Hydrogen Bonding in Primary Amides

• Primary amides can form hydrogen bonds:

  • With other amides.

  • With water, leading to solubility in water if they have < 5 carbons.

Page 15: Hydrogen Bonding in Secondary Amides

• Secondary amides have lower melting points due to fewer hydrogen bonds compared to primary amides.

• They remain soluble in water when < 5 carbons are present.

Page 16: Hydrogen Bonding in Tertiary Amides

• Tertiary amides have the lowest melting points because they form the least hydrogen bonds.

• They can only engage in one hydrogen bond.

Page 17: Chemistry Link to Health: Urea

• Urea: The simplest natural amide, product of protein metabolism.

• It is excreted in urine; failure to excrete can lead to uremia, a toxic buildup in the body.

Page 18: Chemistry Link to Health: Aspirin Substitutes

• Aspirin substitutes like phenacetin and acetaminophen are amides that reduce fever and pain, with minimal anti-inflammatory properties.

Page 19: Chemistry Link to Health: Barbiturates

• Barbiturates: Cyclic amides derived from barbituric acid.

• They act as sedatives in low doses and induce sleep in higher doses but are habit-forming.

• Examples include phenobarbital (Luminal) and pentobarbital (Nembutal).