1 / 16

Advanced Higher Chemistry Unit 3 Amines

Advanced Higher Chemistry Unit 3 Amines. secondary. tertiary. primary. Amines. Based on the ammonia molecule where one or more of the hydrogens have been replaced by an alkyl or aryl group. An aryl group is one based on benzene).

edolie
Download Presentation

Advanced Higher Chemistry Unit 3 Amines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Advanced Higher Chemistry Unit 3 Amines

  2. secondary tertiary primary Amines • Based on the ammonia molecule where one or more of the hydrogens have been replaced by an alkyl or aryl group. An aryl group is one based on benzene) • Naming can be confusing as there is more than one acceptable method

  3. Naming amines • Primary amines can be named in two ways: 1. by removing ‘e’ from the name of the parent hydrocarbon and adding the suffix ‘-amine’. e.g. C2H5NH2 ethanamine 2. by adding the suffix ‘-amine’ to the name for the substituent group R e.g. C2H5NH2 ethylamine

  4. propylamine (most common) OR propanamine

  5. The second method is used commonly for simple amines and has the advantage that it makes the naming of secondary and tertiary amines much simpler. • NOTE If the NH2 group is not the principal group in the compound, it is named by the prefix ‘amino’. e.g. CH3CH(NH2)COOH 2-aminopropanoic acid

  6. Secondary and tertiary amines are named by citing the substituent group R preceded by the prefix ‘di’ or ‘tri’ respectively. e.g. butyldimethylamine

  7. Hydrogen bonding occurs in primary and secondary amines (no N-H bond in tertiary), resulting in • Higher boiling points • Increased solubility in water (lower tertiary amines are also soluble as the lone pair on the nitrogen can form H-bonds with water) • Solubility decreases as no. of C’s increase.

  8. Bonding in Amines • All bonds in amines are sigma bonds (see Bonding in Alkanes). Synthesis of Amines • See ‘Halogenalkanes – Synthesis of Amines’

  9. The orientation of the bonds attached to the nitrogen atom has an important bearing on the chemistry of amines. • The ammonia molecule is pyramidal with a lone pair of electrons on the nitrogen atom. • A similar arrangement of bonds will occur around the nitrogen atom in any amine molecule.

  10. Reactions of Amines Amines are weak bases, solutions of amines are weakly alkaline.

  11. If a bottle of conc. HCl is opened near an open bottle of conc. NH3 solution, dense white fumes of NH4Cl are produced. • The NH3 molecule is acting as a base by accepting a hydrogen ion (proton). • The lone pair is used to form a dative covalent bond in which both shared electrons come from the same atom. • The HCl acts as an acid by donating a proton.

  12. A similar result is obtained if ethyl amine is used instead of ammonia

  13. C2H5NH2(aq) + H+Cl–(aq) C2H5NH3+Cl–(aq) ethylamine ethylammonium chloride

  14. The above reaction can be used to separate amines from organic mixtures • Add HCl(aq) to mixture • Add and shake with a relatively non-polar solvent (e.g. ethoxyethane) • Non basic-compounds will dissolve in organic solvent • Amine salt will remain in aqueous layer • Original amine can be regenerated by heating with NaOH C2H5NH3+Cl–(aq) + Na+OH–(aq) Na+Cl–(aq) + H2O(l) + C2H5NH2(g)

  15. Reaction of amines with carboxylic acids is the first step in the formation of amides (see ‘Reactions of Carboxylic Acids’)

  16. Exercise • Now try the exercise on page 48 of your Unit 3(b) notes.

More Related