keto acid

Examples of keto acid in the following topics:

• Pyruvic Acid and Metabolism

  • Pyruvic acid (CH3COCOOH) is an organic acid, a ketone, and the simplest of the alpha-keto acids.
  • Pyruvic acid (CH3COCOOH; is an organic acid, a ketone, and the simplest of the alpha-keto acids.
  • The carboxylate (COO−) anion of pyruvic acid.
  • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration); when oxygen is lacking, it ferments to produce lactic acid.
  • The cycle is also known as the citric acid cycle or tri-carboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions.

• Connecting Proteins to Glucose Metabolism

  • However, if there are excess amino acids, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism.
  • The remaining atoms of the amino acid result in a keto acid: a carbon chain with one ketone and one carboxylic acid group.
  • The keto acid can then enter the citric acid cycle.
  • When deaminated, amino acids can enter the pathways of glucose metabolism as pyruvate, acetyl CoA, or several components of the citric acid cycle.
  • The carbon skeletons of certain amino acids (indicated in boxes) are derived from proteins and can feed into pyruvate, acetyl CoA, and the citric acid cycle.

• Absorptive State

  • This main product of fat digestion is first broken down to fatty acids and glycerol through hydrolysis using lipoprotein lipase.
  • The liver deaminates amino acids to keto acids to be used in the Kreb's cycle in order to generate energy in the form of ATP.

• Types of Catabolism

  • Fats are catabolised by hydrolysis to free fatty acids and glycerol.
  • The glycerol initiates glycolysis and the fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle.
  • The amino group is fed into the urea cycle, leaving a deaminated carbon skeleton in the form of a keto acid.
  • Several of these keto acids are intermediates in the citric acid cycle, for example the deamination of glutamate forms α-ketoglutarate.
  • The glucogenic amino acids can also be converted into glucose, through gluconeogenesis.

• Reductions & Oxidations of Carboxylic Acids

  • Sodium borohydride, NaBH4, does not reduce carboxylic acids; however, hydrogen gas is liberated and salts of the acid are formed.
  • Partial reduction of carboxylic acids directly to aldehydes is not possible, but such conversions have been achieved in two steps by way of certain carboxyl derivatives.
  • Lead tetraacetate will also oxidize mono-carboxylic acids in a manner similar to reaction #1.
  • Finally, the third example illustrates the general decarboxylation of β-keto acids, which leaves the organic residue in a reduced state (note that the CO2 carbon has increased its oxidation state. ).
  • Also, various iodide derivatives may be prepared directly from the corresponding carboxylic acids.

• Amino Acid Synthesis

  • These polymers are linear and unbranched, with each amino acid within the chain attached to two neighboring amino acids.
  • Twenty-two amino acids are naturally incorporated into polypeptides and are called proteinogenic or natural amino acids.
  • All amino acids are synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway.
  • Amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid.
  • Examples include lanthionine, 2-aminoisobutyric acid, dehydroalanine, and the neurotransmitter gamma-aminobutyric acid.

• Mechanism of Electrophilic α-Substitution

  • (iv) Enolization is catalyzed by acids and bases.
  • A full description of the acid and base-catalyzed keto-enol tautomerization process (shown below) discloses that only two intermediate species satisfy this requirement.
  • These are the enol tautomer itself and its conjugate base (common with that of the keto tautomer), usually referred to as an enolate anion.
  • Together with some related acidities, this is listed in the following table.
  • Even though enol tautomers are about a million times more acidic than their keto isomers, their low concentration makes this feature relatively unimportant for many simple aldehydes and ketones.

• Aldehydes and Ketones

  • Ketones have alpha-hydrogens which participate in keto-enol tautomerism.
  • The keto form predominates at equilibrium for most ketones.
  • The interconversion can be catalyzed by the presence of either an acid or a base.
  • In the presence of strong oxidizing agents, they can be oxidized to carboxylic acids.
  • The interconversion between the two forms can be catalyzed by an acid or a base.

• Hydration of Alkynes and Tautomerism

  • As with alkenes, the addition of water to alkynes requires a strong acid, usually sulfuric acid, and is facilitated by mercuric sulfate.
  • The explanation for this deviation lies in enol-keto tautomerization, illustrated by the following equation.
  • Tautomeric equilibria are catalyzed by traces of acids or bases that are generally present in most chemical samples.
  • Two factors have an important influence on the enol-keto tautomerizations described here.
  • The keto tautomer has a 17.5 kcal/mole advantage in bond energy, so its predominance at equilibrium is expected.

• The Aldol Reaction

  • Stepwise mechanisms for the base-catalyzed and acid-catalyzed reactions are seen in the third and fourth diagrams below.
  • The dehydration step of an aldol condensation is also reversible in the presence of acid and base catalysts.
  • The acid-catalyzed elimination of water is not exceptional, since this was noted as a common reaction of alcohols.
  • As shown by the equations, these eliminations might proceed from either the keto or enol tautomers of the beta-hydroxy aldol product.
  • Although the keto tautomer route is not unreasonable (recall the enhanced acidity of the alpha-hydrogens in carbonyl compounds), the enol tautomer provides a more favorable pathway for both acid and base-catalyzed elimination of the beta oxygen.