Carbonyl Compounds We just keep going, and going, and going

Carbonyl Couponds Compound that contains a carbonyl function group (C=O) – Aldehyde – Ketone – Carboxylic acid – Ester – Acyl chloride – Amide – Peptide

Aldehyde Compound where the carbonyl group is located at the end of the molecule Nomenclature: – Like alcohols end with “-ol”, aldehydes end with “-al” General Formula: – R- CHO Example: – CH 3 CH 2 CHO – propanal

Ketone Compound where the carbonyl group is located in the middle of a carbon chain Nomenclature: – Drop the last “e” and end the name with “-one” – A number location goes directly before the suffix i.e. pentan-2-one VS pentan-3-one General Formula: – R- CO –R’ Example: – CH 3 COCH 3 – propanone

Physical Properties of Aldehydes and Ketones Both are polar molecules, so: – Have higher melting and boiling points than corresponding alkanes Melting and boiling points increase with molar mass (as London dispersion forces increases) Both can form Hydrogen bonds with water molecules – Low molar mass aldehydes and ketones (3 carbons or less) are soluble in water Also can have long non-polar carbon chains: soluble in non-polar solvents

Chemical Properties of Aldehydes and Ketones Oxidation Reactions – Aldehydes easily oxidised to Carboxylic Acids – Ketones cannot be oxidised Great way to tell them apart. Added ReagentObservations (for aldehyde) Acidified potassium dichromateOrange sol’n turns green Tollens’ reagentBlack precipitate (of silver) or silver mirror Fehling’s/Benedict’s solutionBlue solution forms orange/red

Chemical Properties of Aldehydes and Ketones Reduction reaction with sodium borohydride, NaBH 4 – Turns the carbonyl compound to an alcohol Aldehydes: primary alcohol Ketones: secondary alcohol

Carbonyl Compounds …and going and going and going …

Carboxylic Acids Compound where the carbonyl group is located at the end of the molecule (like aldehydes), but there is also and hydroxide group (-OH) and the same end Nomenclature: – Drop the last “e” and end the name with “-oic acid” Carboxylates – salts of carboxylic acids (CH 3 CH 2 COONa) General Formula: – R- COOH Example: – CH 3 CH 2 COOH – Propanoic acid

Physical Properties of Carboxylic Acids Highly polar w/ Hydrogen bonding – Higher melting and boiling points than corresponding alkanes – Straight-chain carboxylic acids (up to 10 carbons) are liquid at room temp (due to strong IMF) – Small carboxylic acids (4 carbons or less) are soluble in water

Chemical Properties of Carboxylic Acids Acidic Reactions – Weak acids, so they partialy dissociate in water – Forms a hydronium ion and a Carboxylate Ion CH 3 CH 2 COOH + H 2 O  CH 3 CH 2 COO - + H 3 O + – Show acidic properties Turns blue litmus red Conduct electricity (not as well as strong acids) React with bases to form carboxylate salt and water React slowly with metals to form carboxylate salt and H 2 (g) React with carbonates and hydrogen carbonates to form carboxylate salt, water, and carbon dioxide gas

Chemical Properties of Carboxylic Acids Chlorination – A chlorine is somehow added in to the mix – Carboxylic acid + SOCl 2  a substition reaction The –OH group is replaced by a chlorine (forming an acyl chloride)

Chemical Properties of Carboxylic Acids Esterificatio Who wants to guess what is made? An ester, that’s right :P A condensation reaction: carboxylic acid + alcohol (using H 2 SO 4 )  ester – “-OH” is removed from the acid and “-H” is taken off the “-OH” of the alcohol, leaving an ester and a water