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Nomenclature of Carboxylic Acid Derivatives Acid Halide Substituents

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Nomenclature of Carboxylic Acid Derivatives Acid Halide Substituents Gentilucci, Carboxylic Acid Derivatives Nomenclature of Carboxylic Acid Derivatives Gentilucci, Carboxylic Acid Derivatives Acid halides 1. Alkane + the suffix -oyl followed by the halogen. 2. Select the longest continuous carbon chain, containing the acyl group. 3. Number the carbon chain, beginning at the end nearest to the acyl group. 4. Number the substituents and write the name, listing substituents alphabetically. Acid halide substituents attached to rings are named using the suffix - carbonyl. 1 Gentilucci, Carboxylic Acid Derivatives Anhydrides 1. Symmetrical: replace the ending "acid" with "anhydride ". 2. Asymmetrical: select the longest continuous carbon chain, containing the carboxylic acid group, and derive the parent name by replacing the -e ending with -oic anhydride . 3. Number the carbon chain, beginning at the end nearest to the acyl group. 4. Number the substituents and write the name, listing substituents alphabetically. Gentilucci, Carboxylic Acid Derivatives Amides are named by replacing the ending -oic acid with -amide . 1. Select the longest continuous carbon chain, containing the acyl group, and derive the parent name by replacing the -e ending with -amide . 2. Number the carbon chain, beginning at the end nearest to the acyl group. 3. Number the substituents and write the name, listing substituents alphabetically. 4. If the nitrogen atom is further substituted, the substituents are preceded by N- to indicate that they are attached to the nitrogen. Acid halide substituents attached to rings are named using the suffix - carboxamide. 2 Gentilucci, Carboxylic Acid Derivatives Carboxylate esters 1. Select the longest continuous carbon chain containing the acyl group, and derive the parent name by replacing the -e ending with –oate . 2. Name the alcohol portion first . 3. Number the carbon chain, beginning at the end nearest to the acyl group. 4. Number the substituents and write the name, listing substituents alphabetically. Acid halide substituents attached to rings are named using the suffix -carboxylate. Gentilucci, Carboxylic Acid Derivatives Nitriles 1. Select the longest continuous carbon chain, containing the nitrile, and derive the parent name by appending –nitrile . 2. Number the carbon chain, beginning at the end nearest to the nitrile group. 3. Number the substituents and write the name, listing substituents alphabetically. Acid halide substituents attached to rings are named using the suffix - carbonitrile. 3 Gentilucci, Carboxylic Acid Derivatives βββ-lactam antibiotics clavulanic acid amoxicillin Phosphoric esters ATP adenosine 5'-triphosphate transports chemical energy within cells. It is produced as an energy source during the processes of photosynthesis and cellular respiration. Gentilucci, Carboxylic Acid Derivatives Thioesters AcCoA carboxylase / Biotin HCO3- / ATP Ac-CoA 4 Gentilucci, Carboxylic Acid Derivatives Fatty acid biosynthesis + Ac-CoA + 7 malonyl-CoA + 14 NADPH palmitate + 7 CO 2 + 14 NADP + 8 CoA Gentilucci, Carboxylic Acid Derivatives Reactions of Carboxylic −δ Acid Derivatives The attack of a nucleophile on an acyl derivative results in the formation of a transient +δ tetrahedral intermediate. For simple acyl derivatives, it is possible to apply a simple set of rules to determine which group around the tetrahedral center is the "best leaving group", and hence, what will be the predominate Weaker base = best leaving group product of a given reaction. 5 Gentilucci, Carboxylic Acid Derivatives Example. The potential leaving groups are methoxide and phenoxide. The conjugate acids of methoxide and phenolate anions are methanol, pKa=16, and phenol, pKa=9. The strongest acid is phenol, and the major product formed will be ethyl acetate. Gentilucci, Carboxylic Acid Derivatives Another example. In summary, starting from an acyl chloride it is possible to prepare a phenyl acetate, while starting from an ester, phenyl acetate is obtained only in traces. Reactivity : acid chlorides > anhydrides > esters > amides 6 Gentilucci, Carboxylic Acid Derivatives Acid Halides hydrolysis Acid halides are the most reactive acyl derivatives (Cl- is an excellent g group), and can be readily converted into carboxylic acids, esters and amides, by simple reaction with the appropriate nucleophile. The reaction involves an addition- elimination mechanism Gentilucci, Carboxylic Acid Derivatives Reaction of acid halides with Grignard reagents, or reduction with LiAlH 4, leads to the incorporation of two moles of Grignard (or hydride), in a mechanism which involves an intermediate aldehyde or ketone. When a bulky reducing agent, such as lithium tri- tert-butoxylaluminum hydride is utilized, the reduction or acyl halides can be stopped at the intermediate aldehyde. 7 Gentilucci, Carboxylic Acid Derivatives hydrolysis Acid Anhydrides Acid halides are the next most reactive acyl derivatives (leaving group = CH 3COO-). As with acid halides, reduction of anhydrides with LiAlH 4 results in the addition of two moles of hydride, forming the primary alcohol Gentilucci, Carboxylic Acid Derivatives Hydrolysis – Esters saponification Less reactive respect acid chlorides and anhydrides due to the electron delocalization effect of OR group (see amides). Moderate stability in H2O. LiAlH3 + + ROH’ transesterification 8 Gentilucci, Carboxylic Acid Derivatives Amides Amides are relatively unreactive largely because the electrons from the adjacent nitrogen participate in resonance delocalization with the adjacent carbonyl, making the carbonyl carbon significantly less electropositive. Amides undergo acid-catalyzed hydrolysis to give carboxylic acids. Unsubstituted amides also undergo dehydration in the presence of SOCl 2 to give the corresponding nitrile. Gentilucci, Carboxylic Acid Derivatives Nitriles The reaction with Grignard reagent involves nucleophilic attack on the nitrile carbon to give an anionic intermediate which is resistant to further attack, and undergoes hydrolysis to give a ketone. Reduction with DIBAH (diisobutylaluminum hydride) follows a similar mechanism. 9.
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