Chem 2412 Additional Nomenclature

1. Chem 2412 Additional Nomenclature

2. The Importance of Carboxylic Acids (RCO2H) • Starting materials for acyl derivatives (esters, amides, and acid chlorides) • Abundant in nature from oxidation of aldehydes and alcohols in metabolism • Acetic acid, CH3CO2H, - vinegar • Butanoic acid, CH3CH2CH2CO2H (rancid butter) • Long-chain aliphatic acids from the breakdown of fats

3. Functional Group Priority • Carboxylic Acids (3 O bonds, 1 OH) • Esters (3 O bonds, 1 OR) • Amides • Nitriles • Aldehydes (2 O bonds, 1H) • Ketones (2 O bonds) • Alcohols (1 O bond, 1 OH) • Thiols • Amines • Alkenes, Alkynes • Alkanes • Ethers • Halides The parent will be determined based on the highest priority functional group.

4. 20.1 Naming Carboxylic Acids and Nitriles • Carboxylic Acids, RCO2H • If derived from open-chain alkanes, replace the terminal -e of the alkane name with -oic acid • The carboxyl carbon atom is C1

5. Alternative Names • Compounds with –CO2H bonded to a ring are named using the suffix -carboxylic acid • The CO2H carbon is not itself numbered in this system • Use common names for formic acid (HCOOH) and acetic acid (CH3COOH) – see Table 20.1

6. Nitriles, RCN • Closely related to carboxylic acids named by adding -nitrile as a suffix to the alkane name, with the nitrile carbon numbered C1 • Complex nitriles are acids; named as derivatives of carboxylic acids. • Replace -ic acid or -oic acid ending with -onitrile

7. 20.2 Structure and Properties of Carboxylic Acids • Carboxyl carbon sp2 hybridized: carboxylic acid groups are planar with C–C=O and O=C–O bond angles of approximately 120° • Carboxylic acids form hydrogen bonds, existing as cyclic dimers held together by two hydrogen bonds • Strong hydrogen bonding causes much higher boiling points than the corresponding alcohols

8. Dissociation of Carboxylic Acids • Carboxylic acids are proton donors toward weak and strong bases, producing metal carboxylate salts, RCO2+M • Carboxylic acids with more than six carbons are only slightly soluble in water, but their conjugate base salts are water-soluble

9. Acidity Constant and pKa • Carboxylic acids transfer a proton to water to give H3O+ and carboxylate anions, RCO2, but H3O+ is a much stronger acid • The acidity constant, Ka,, is about 10-5 for a typical carboxylic acid (pKa ~ 5)

10. Substituent Effects on Acidity • Electronegative substituents promote formation of the carboxylate ion

11. Inductive Effects on Acidity • Fluoroacetic, chloroacetic, bromoacetic, and iodoacetic acids are stronger acids than acetic acid • Multiple electronegative substituents have synergistic effects on acidity

12. Carboxylic Compounds • Acyl group bonded to X, an electronegative atom or leaving group • Includes: X = halide (acid halides), acyloxy (anhydrides), alkoxy (esters), amine (amides), thiolate (thioesters), phosphate (acyl phosphates)

13. General Reaction Pattern • Nucleophilic acyl substitution Why this Chapter? • Carboxylic acids are among the most widespread of molecules. • A study of them and their primary reaction “nucleophilic acyl substitution” is fundamental to understanding organic chemistry

14. 21.1 Naming Carboxylic Acid Derivatives • Acid Halides, RCOX • Derived from the carboxylic acid name by replacing the -ic acid ending with -yl or the -carboxylic acid ending with –carbonyl and specifying the halide

15. Naming Acid Anhydrides, RCO2COR' • If symmetrical replace “acid” with “anhydride” based on the related carboxylic acid • Unsymmetrical anhydrides— cite the two acids alphabetically

16. Naming Amides, RCONH2 • With unsubstituted NH2 group. replace -oic acid or -ic acid with -amide, or by replacing the -carboxylic acid ending with –carboxamide • If the Nis further substituted, identify the substituent groups (preceded by “N”) and then the parent amide

17. Naming Amides N,N-dimethylethanamide N-isobutylmethylbutanamide N,2-dimethylbenzamide N-ethyl-N-phenylbenzamide

18. Naming Esters, RCO2R’ • Name R’ and then, after a space, the carboxylic acid (RCOOH), with the “-ic acid” ending replaced by “-ate”

19. Naming Esters • Esters may have common or IUPAC names • The first word of the name of an ester is the name of alkyl or aromatic group (R) • Change the –ic acid ending of the acid name to –ate (like naming carboxylic acid salts) • Parent contains the –COO group methyl ethanoate phenyl butanoate ethyl benzoate isopropyl methanoate methyl benzoate

20. IUPAC Names – Simple Amines • For simple amines, the suffix -amine is added to the name of the alkyl substituent

21. IUPAC Names – “-amine” Suffix • Replace –e in alkane with –amine. • Number position of amino group lowest on parent chain. • If substituent on nitrogen, prefixed with N. 3-Pentanamine 3-Methyl-1-butanamine 2-Hexanamine N,N-Dimethyl-2-hexanamine N-Methyl-2-butanamine N-Methyl-2-hexanamine 2,5-hexanediamine cyclohexylamine N-Ethyl-N-methyl-2-hexanamine

22. IUPAC Names – Amines with More Than One Functional Group • Consider the –NH2 as an amino substituent on the parent molecule

23. IUPAC Names – Multiple Alkyl Groups • Symmetrical secondary and tertiary amines are named by adding the prefix di- or tri- to the alkyl group

24. IUPAC Names – Multiple, Different Alkyl Groups • Named as N-substituted primary amines • Largest alkyl group is the parent name, and other alkyl groups are considered N-substituents

25. Common Names of Heterocyclic Amines • If the nitrogen atom occurs as part of a ring, the compound is designated as being heterocyclic • Each ring system has its own parent name

26. 15.1 Naming Aromatic Compounds • Many common names (toluene = methylbenzene; aniline = aminobenzene) • Monosubstituted benzenes systematic names as hydrocarbons with –benzene • C6H5Br = bromobenzene • C6H5NO2 = nitrobenzene, and C6H5CH2CH2CH3 is propylbenzene

27. Aromatics • 6 C ring structures with alternating double bonds (benzene). • Everything that is not aromatic, is aliphatic (alkanes, alkenes, alkynes). • Early problem chemists found was that benzene was not reactive (recall that alkenes are reactive due to double bond). • Kekule proposed that double bonds alternated between 2 equivalent structures • electrons move around a conjugated pi bond system of rings • Stabilizes structure and makes it less reactive.

28. Naming Benzene Derivatives • For single replacement (H some FG), cmpd named as a benzene derivative.

29. Naming Benzene Derivatives (Continued) Some common names are IUPAC-accepted and used preferentially.

30. Naming Benzene Derivatives (Continued) • With only 2 groups on benzene ring, can use o, m, p (ortho, meta, para) nomenclature.

31. Naming Benzenes with More Than Two Substituents • Choose numbers to get lowest possible values • List substituents alphabetically with hyphenated numbers • Common names, such as “toluene” can serve as root name (as in TNT)

32. The Phenyl Group • When a benzene ring is a substituent, the term phenyl is used (for C6H5?) • You may also see “Ph” or “f” in place of “C6H5” • “Benzyl” refers to “C6H5CH2?”

33. Benzene as a Phenyl group • The benzene ring can also be an attached substituent group.