Organic Oxygen Compounds Class: acid, formula R—CO—O—H Class: ester, formula R—CO—O—R’

Carboxylic acids Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the  formula -C(=O)OH, usually written -COOH or -CO2H.  Carboxylic acids: R-COOH, R-CO2H,

NOMENCLATURE In IUPAC nomenclature, the name of a carboxylic acid is obtained by changing the -e of the corresponding parent alkane to -oic acid. The common names for many carboxylic acids remain in use Methanoic and ethanoic acid are usually referred to as formic and acetic acid

trifluoroethanoic acid Nomenclature formula IUPAC name traditional name HCOOH methanoic acid formic acid CH3-COOH ethanoic acid acetic acid CH3CH2-COOH propanoic acid propionic acid CH2=CH-COOH propenoic acid acrylic acid CF3-COOH trifluoroethanoic acid

How do you name CARBOXYLIC ACIDS?

give a name …

Common names All common names of acid end in –ic acid. Positions of substituent's on the chain are labeled with Greek letters. 5 4 3 2 1 C—C—C—C—C=O δ γ β α used in common names

Carboxylic acids, common names: … CH3(CH2)4CO2H caproic acid L. caper goat CH3(CH2)5CO2H --- CH3(CH2)6CO2H caprylic acid CH3(CH2)7CO2H --- CH3(CH2)8CO2H capric acid CH3(CH2)9CO2H --- CH3(CH2)10CO2H lauric acid oil of lauryl

special names

IUPAC nomenclature for carboxylic acids: parent chain = longest, continuous carbon chain that contains the carboxyl group  alkane, drop –e, add –oic acid HCOOH methanoic acid CH3CO2H ethanoic acid CH3CH2CO2H propanoic acid CH3 CH3CHCOOH 2-methylpropanoic acid Br CH3CH2CHCO2H 2-bromobutanoic acid

dicarboxylic acids: HOOC-COOH oxalic acid HO2C-CH2-CO2H malonic acid HO2C-CH2CH2-CO2H succinic acid HO2C-CH2CH2CH2-CO2H glutaric acid HOOC-(CH2)4-COOH adipic acid HOOC-(CH2)5-COOH pimelic acid Oh, my! Such good apple pie!

salts of carboxylic acids: name of cation + name of acid: drop –ic acid, add –ate CH3CO2Na sodium acetate or sodium ethanoate CH3CH2CH2CO2NH4 ammonium butyrate ammonium butanoate (CH3CH2COO)2Mg magnesium propionate magnesium propanoate

polar + hydrogen bond  relatively high mp/bp water insoluble physical properties: polar + hydrogen bond  relatively high mp/bp water insoluble exceptions: four carbons or less acidic turn blue litmus  red soluble in 5% NaOH RCO2H + NaOH  RCO2-Na+ + H2O stronger stronger weaker weaker acid base base acid

RCO2H RCO2- covalent ionic water insoluble water soluble Carboxylic acids are insoluble in water, but soluble in 5% NaOH. Identification. Separation of carboxylic acids from basic/neutral organic compounds. The carboxylic acid can be extracted with aq. NaOH and then regenerated by the addition of strong acid.

RMgX + CO2  RCO2MgX + H+  RCOOH Carboxylic acids, syntheses: oxidation of primary alcohols RCH2OH + K2Cr2O7  RCOOH 2. oxidation of arenes ArR + KMnO4, heat  ArCOOH 3. carbonation of Grignard reagents RMgX + CO2  RCO2MgX + H+  RCOOH 4. hydrolysis of nitriles RCN + H2O, H+, heat  RCOOH

Carboxylic acids, reactions: as acids conversion into functional derivatives a)  acid chlorides b)  esters c)  amides reduction alpha-halogenation

Why are carboxylic acids acidic? Using the definition of an acid as a "substance which donates protons (hydrogen ions) to other things", the carboxylic acids are acidic because of the hydrogen in the -COOH group. In solution in water, a hydrogen ion is transferred from the -COOH group to a water molecule. For example, with ethanoic acid, you get an ethanoate ion formed together with a hydroxonium ion, H3O+.

as acids: with active metals RCO2H + Na  RCO2-Na+ + H2(g) with bases RCO2H + NaOH  RCO2-Na+ + H2O quantitative HA + H2O  H3O+ + A- ionization in water Ka = [H3O+] [A-] / [HA]

Conversion into functional derivatives:  acid chlorides

 esters “direct” esterification: H+ RCOOH + R´OH  RCO2R´ + H2O -reversible and often does not favor the ester -use an excess of the alcohol or acid to shift equilibrium -or remove the products to shift equilibrium to completion “indirect” esterification: RCOOH + PCl3  RCOCl + R´OH  RCO2R´ -convert the acid into the acid chloride first; not reversible

 amides “indirect” only! RCOOH + SOCl2  RCOCl + NH3  RCONH2 amide Directly reacting ammonia with a carboxylic acid results in an ammonium salt: RCOOH + NH3  RCOO-NH4+ acid base

Reduction: RCO2H + LiAlH4; then H+  RCH2OH 1o alcohol Carboxylic acids resist catalytic reduction under normal conditions. RCOOH + H2, Ni  NR

Alpha-halogenation: (Hell-Volhard-Zelinsky reaction) RCH2COOH + X2, P  RCHCOOH + HX X α-haloacid X2 = Cl2, Br2

DERIVATIVES OF CARBOXYLIC ACIDS ESTERS What are esters? Esters are derived from carboxylic acids. A carboxylic acid contains the -COOH group, and in an ester the hydrogen in this group is replaced by a hydrocarbon group of some kind. This could be an alkyl group like methyl or ethyl, or one containing a benzene ring like phenyl.

A common ester - ethyl ethanoate Notice that the ester is named the opposite way around from the way the formula is written. The "ethanoate" bit comes from ethanoic acid. The "ethyl" bit comes from the ethyl group on the end.

A few more esters ...

Esters are very common natural products also called "isopentyl acetate" and "isoamyl acetate" contributes to characteristic odor of BANANAS

Esters of Glycerol R, R', and R" can be the same or different called "triacylglycerols," "glyceryl triesters," or "triglycerides"

Esters of Glycerol fats and oils are mixtures of glyceryl triesters

Fats and oils Differences between fats and oils Animal and vegetable fats and oils are just big complicated esters. The difference between a fat (like butter) and an oil (like sunflower oil) is simply in the melting points of the mixture of esters they contain. If the melting points are below room temperature, it will be a liquid - an oil. If the melting points are above room temperature, it will be a solid - a fat.

Saturated and unsaturated fats and oils If the fat or oil is saturated, it means that the acid that it was derived from has no carbon-carbon double bonds in its chain. Stearic acid is a saturated acid, and so glyceryl tristearate is a saturated fat. Those same terms will then apply to the esters that are formed

Here is a simplified diagram of a saturated fat:

Saturated and unsaturated fats and oils If the acid has just one carbon-carbon double bond somewhere in the chain, it is called mono-unsaturated. If it has more than one carbon-carbon double bond, it is polyunsaturated. Those same terms will then apply to the esters that are formed.

Oleic acid is a typical mono-unsaturated acid . . . and linoleic and linolenic acids are typical polyunsaturated acids

Here is a simplified diagram of a unsaturated fats: Unsaturated fats and oils have at least one carbon-carbon double bond in at least one chain.

You might possibly have come across the terms "omega 6" and "omega 3" in the context of fats and oils. Linoleic acid is an omega 6 acid. It just means that the first carbon-carbon double bond starts on the sixth carbon from the CH3 end. Linolenic acid is an omega 3 acid for the same reason. Because of their relationship with fats and oils, all of the acids above are sometimes described as fatty acids.

"omega 3“ acid Chemical structure of eicosapentaenoic acid (EPA) Chemical structure of  docosahexaenoic acid (EPA)

The physical properties of fats and oils Solubility in water Melting points None of these molecules are water soluble. The chain lengths are now so great that far too many hydrogen bonds between water molecules would have to be broken - so it isn't energetically profitable. The melting points determine whether the substance is a fat (a solid at room temperature) or an oil (a liquid at room temperature). Fats normally contain saturated chains. The greater the extent of the unsaturation in the molecules, the lower the melting points.