Carboxylic Acids & Derivatives (Esters, Amides, Phosphoric Acid Ester)

1. Carboxylic Acids & Derivatives (Esters, Amides, Phosphoric Acid Ester)

2. Carboxylic Acids and Their Derivatives: Properties and Names • Caboxylic acids have an –OH group bonded to a carbonyl group. • In their derivatives, OH is substituted by other group. Such as, • Esters have a –OR group bonded to a carbonyl group. • Amides have an –NH2 group bonded to a carbonyl group.

3. Carboxylic Acid & Derivatives Cont. • all contain polar functional group because of the C=O (as a result they have higher boiling points than alkanes) • all participate in carbonyl-group substitution reaction, in which the group bonded to the carbonyl group is replaced by another group • The part of molecules in which an alkyl group is bonded to the carbonyl carbon atom is known as an acyl group, RC=O.

4. Substitution Reactions O O ║ ║ R – C – OH + HZ R – C – Z + H– OH -OR’ -OR’ -NH2 -NH2 -NHR’ -NHR’ -NR’2 -NR’2

5. Properties of Carboxylic Acids • Carboxylic acids can donate proton (H+) to bases. • Carboxylic acids hydrogen bond with each other. As a result of hydrogen bonding, they have higher boiling points than similar alkanes.

6. Properties Cont. • Carboxylic acids have sharp and strong odor. • Carboxylic acids with up to 4 carbons are water soluble. • Water solubility decreases as the size of the alkyl group increases. • Acids with larger saturated alkyl groups are waxy, odorless solids.

7. Naming Carboxylic Acids • Carboxylic acids are named systematically (IUPAC) by replacing the “–e” at the end of the alkane name with “–oic acid”. If alkyl or other substituents are present, the chain is numbered beginning at the –COOH end. • Dicarboxylic acids (contains two – COOH groups) are named by adding the ending “–dioic acid” to the alkane name. • Unsaturated acids are named systematically in the IUPAC system with the ending “–enoic acid”.

8. Naming Carboxylic Acids • count number of carbons in chain • use “-oic acid” ending CH3CH2COOH propanoic acid CH3 CH3CHCH2COOH 3-methylbutanoic acid HOOCCH2CH2COOH butanedioic acid (succinic acid) (2 carboxylic acid groups, so “dioic”)

9. Some Common Carboxylic Acids butyric acid (rancid butter) citric acid (citrus fruits) O O OH O ║ ║ ׀ ║ CH3CH2CH2 – C – OH HOCCH2CCH2COH ׀ acetic acid (in vinegar) C = O O ׀ ║ OH CH3C – OH

10. Acidity of Carboxylic Acids • Carboxylic acids are weak acids. • Acid strengths of common carboxylic acids are about the same as that for acetic acid (Ka = 1.8 x 10-5). • Carboxylic acids undergo neutralization reactions with bases and produce water and a carboxylic acid salt. • The sodium and potassium salts of carboxylic acids are ionic solids that are more soluble in water than the carboxylic acids themselves.

11. Neutralization of Carboxylic Acids • undergo neutralization reactions with bases like other acids CH3COOH + NaOH  CH3COO-Na+ + H2O acetic acid sodium sodium acetate hydroxide (a carboxylate salt or carboxylic acid salt)

12. Carboxylic Acid O ║ R – C – OH easily converted to ester Ester O ║ R – C – O – R’ easily converted to carboxylic acid Carboxylic Acid & Esters

13. name 2nd name 1st carbons so buty Naming Esters • two parts to name • name the alkyl group (R) in the ester portion (-COOR) • name the parent portion with an “-ate” ending R’COOR O CH3CH2CH2COCH3 methyl butyrate methyl

14. Esters • lower boiling point than the acid from which it is derived (because ability to hydrogen-bond with each other is lost) O O O ║ ║ ║ CH3COH CH3COCH3 CH3COCH2CH3 bp. 118 °C bp 57 °C bp 77 °C (acetic acid) (methyl ester) (ethyl ester)

15. Esters Cont. • simple esters are: • colorless • volatile liquids • have pleasant odors • neither acids nor bases in aqueous solution methyl butyrate simulates the taste of apples the flavor in pineapples are derived from esters

16. Esterification • the reaction between an alcohol and a carboxylic acid to give an ester plus water O CH3CH2CH2COH + HOCH2CH3 butanoic acid ethanol O CH3CH2CH2COCH2CH3 + H2O ethyl butanoate (in pineapple oil) strong acid catalyst (like sulfuric acid) ester formation is favored by using a large excess of alcohol or continuously removing one of the products

17. Aspirin • Willow tree (Salix) bark contains salicin • Salicin converted to salicylic acid • Esterification of salicylic acid gives aspirin.

18. Acetylsalicylic Acid (Aspirin) aspirin is an ester formed between acetic acid and the –OH group of salicylic acid

19. Morphine to Heroin by Acetylation

20. Hydrolysis of Esters • Esters can hydrolyze to give back carboxylic acid plus alcohol. O O ║ ║ R – C – OR’ + H – OH R – C – OH + H – OR’ ester water carboxylic acid alcohol

21. Ester Hydrolysis • acid catalyzed hydrolysis • simply the reverse of esterification • base catalyzed hydrolysis • saponification O O C-OCH2CH3 + H-OH C-OH + HOCH2CH3 O O ║ ║ CH3CH2CH2COCH3 + NaOH(aq)  CH3CH2CH2CO- Na+ + CH3OH methyl butanoate sodium butanoate methanol

22. Aspirin vs. Ibuprofen & Acetaminophen

23. Aspirin • Aspirin: A member of a group of drugs known as salicylates. • Aspirin is an: • analgesic (relief pains), • antipyretic (reduces fever), • anti-inflammatory (reduces inflammation).

24. Acetaminophen • Acetaminophen: An amide that also contain a hydroxyl group. • It is best known as Tylenol. An alternative to Aspirin for pain relief but it unlike aspirin it is not an anti-innflammatory agent.

25. Amides • Amides may contain –NH2 group or one or both of the hydrogen replaced with alkyl groups.

26. Properties of Amides • Unsubstituted amides, RCONH2, can form three hydrogen bonds to other amide molecules • have higher melting and boiling points than the acids from which they are derived. • Monosubstituted amides, RCONHR’, can form hydrogen bonds to other amide molecules. • Disubstituted amides, RCONR’2, can not form hydrogen bonds to other amide molecules • have lower boiling points.

27. Naming Amides • Unsubstituted amides, RCONH2, are named by replacing the “–ic” or “–oic acid” by “–amide”. • Substituted amides are named by first specifying the alkyl group and then identifying the amide name. The alkyl substituents are preceded by the letter N to specify that the alkyl groups are attached to the nitrogen.

28. Example O ║ CH3CH2CN(CH3)2 N,N-dimethylpropamide

29. Reaction of Carboxylic Acid to Form an Amide • Similar to making an ester (where an alcohol reacted with a carboxylic acid). • In this case, an amine react with a carboxylic acid to replace the OH group.

30. Amide Formation Cont. • Unsubstituted amides are formed by warming a mixture of a carboxylic acid and ammonia. O O ║ ║ CH3COH + NH3 ---> CH3CNH2 + HOH • Substituted amides are formed by warming a mixture of a carboxylic acid and a 1° or 2° amine. O O ║ ║ CH3COH + CH3NH2 ---> CH3CNHCH3 + HOH

31. Hydrolysis of Amides • Just like esters, amides undergo hydrolysis to give back the carboxylic acid and an amine. • can be catalyzed by either an acid or a base.

32. Amides are stable in water but undergo hydrolysis when heated in the presence of a base or an acid. The product of amide hydrolysis reaction in the presence of a base or an acid are shown below.

33. Polyamides and Polyesters • Polymer molecules are composed of thousands of repeating units (monomers). • Both polyamides and polyesters are polymer and they have many uses. • Polyamides are formed by reaction between diamines and diacids. • Polyesters are formed by reaction between diacids and dialcohols.

34. Example: Nylon-6,6 hexamethylene diamine adipic acid NH2-(CH2)6-NH2 + HO2C-(CH2)4-CO2H O NH2 -(CH2)6-NH-C-(CH2)4 -CO2H + H2O n nylon-6,6

35. O O N N C C H H Poly(p-phenylene terephthalamide) O O + H2N NH2 ClC CCl p-phenylene diamine terephthaloyl chloride -HCl n

36. Poly(ethylene terephthalate) (PET)Dacron® (fiber) and Mylar® (film)

37. Phosphoric Acid Derivatives • Phosphoric acid is an inorganic acid • has 3 ionizable hydrogen atoms allowing it to form 3 different anions.

38. Phosphoric Acid Cont. • Phosphoric acids react with alcohols to form phosphate esters. • Phosphoric acid produces mono, di, or triester by reacting with 1, 2, or 3 of its alcohol groups respectively.

39. Phosphate mono and diesters are acids because they still contain acidic hydrogen atoms. In biochemical reactions and equations, the phosphate groups are thus written in their ionic forms. • Two molecules of phosphoric acid lose water between them and form a phosphoric acid anhydride. The resulting phosphoric acid anhydride (also an acid) reacts with another molecule of phosphoric acid in a similar reaction to produce a triphosphoric acid.

40. Misc.

41. Misc. • phosphoryl group: the –PO32- group in orgaci phosphates • Transfer of a phosphoryl group, -PO32-, from one molecule to another is known as phosphorylation. • In biochemical reaction, phosphorylation reactions provide energy. Such as ATP, a triphosphate, converting to ADP, a diphosphate, releases energy that is used by other biochemical reactions body.