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Organic compounds containing nitrogen and sulfur Alice Skoumalová.

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Presentation on theme: "Organic compounds containing nitrogen and sulfur Alice Skoumalová."— Presentation transcript:

1 Organic compounds containing nitrogen and sulfur Alice Skoumalová

2 Types of bonds in nitrogen compounds: Nitrogen compounds

3 Nitro compounds: R-NO 2  Hydrogen substituted for NO 2  Originate from nitration of aromatic hydrocarbons (HNO 3 )  Examples: chloramphenicol (antibiotic)trinitrotoluene

4  organic derivates of ammonia  Quaternary ammonium salts  Nitrogen heterocyclic compounds Amines: R-NH 2 -NH 2 -NH- -N-

5 nitrosoamine Properties of amines:  basicity of amines (the unshared pair of electrons on the nitrogen atom)  form hydrogen bonds (the polarity of the carbon-nitrogen bond)  form nitrosoamines (nitrites in food may cause cancer)

6 Importance of amines: The most important organic bases In biochemistry:  Quaternary ammonium salts  Biogenic amines  Amino acids  Proteins  Alkaloids

7 Quaternary ammonium salts: Choline:Acetylcholine: - the constituent of phospholipids (lecithin)- neurotransmiter (parasympathetic nervous system)

8 Acetylcholine 1. The synthesis: from choline and acetyl-CoA in the neurons 2. Hydrolysis: in the synaptict cleft (restores the resting potential in the postsynaptic membrane) - the transmitter of the parasympathetic and sympathetic system, at neuromuscular junctions, involved in learning and memory

9 Biogenic amines:  from amino acids by decarboxylation  constituents of biomolecules, neurotransmitters Amino acidAmineFunction SerineEthanolaminePhospholipids CysteineThyoethanolamineComponent of coenzyme A ThreonineAminopropanolComponent of vitamin B 12 Aspartateβ-AlanineComponent of coenzyme A Glutamateγ-AminobutyrateNeurotransmitter (GABA) HistidineHistamineMediator, neurotransmitter DopaDopamineNeurotransmitter 5-hydroxytryptophanSerotoninMediator, neurotransmitter

10 Biogenic amines – examples:

11 Adrenaline and amphetamines: Catecholamines (adrenaline and noradrenaline)  biogenic amines with catechol group derived from tyrosine  hormones (the adrenal medulla), neurotransmitters (sympathetic nervous system) Amphetamines  mimic the action of catecholamines  stimulate the cortex (abuse)

12 Alkaloids:  naturally occurring chemical compounds containing basic nitrogen atoms  important biological properties Examples: Atropine – blocks acetylcholine receptors Cocaine – stimulative effect Reserpine – sedative Ephedrine – bronchodilator

13 Opium and opiates: = morphine alkaloids  important in medicine, abuse  bind to the opioid receptors Examples: Opium, morphine – analgetic, the immature seed pods of opium poppies Codeine – analgetic, antitussive Heroin – synthesizes from morphine Search similar compounds (without addiction):

14 Amides: R-CO-NH 2  an amino group or substituted amino group bonded to a carbonyl carbon Properties:  not basic (the carbonyl group draws electrons away from the nitrogen)  formation of the peptide bond –NH 2 + HOOC- (enzyme-catalyzed)  The great stability toward hydrolysis (the peptide bond is stable, enzymatic hydrolysis)

15 Important amides in medicine:  asparagine, glutamine  urea, carbamate, creatine  nicotinamide – coenzyme NAD  peptides  barbiturates

16 Asparagine, glutamine: The peptide bond:

17 Carbamate and urea = carbonic acid amides (H 2 CO 3 ) Carbamoyl phosphate - intermediate in: urea cycle the formation of pyrimidines

18 Urea  the end-product of protein metabolism in mammals  produced only in the liver (urea cycle)  soluble in water (excreted in the urine)  electron delocalization → weak acid  biuret test (detection of peptide bonds and urea) - heating - biuret in alkaline environment with Cu 2+ - purple

19 Fate of amino acid nitrogen = urea synthesis: Urea nitrogen from:1. NH aspartate

20 Creatine In muscle metabolism, energy for contraction Creatinine In a nonenzymatic reaction from creatine Excreted in the urine

21 Creatine metabolism:

22 Barbiturates  Barbituric acid derivates:  sedatives, hypnotics, narcotiks

23 Imines: R-C=N-R Schiff bases  functional group that contains a carbon-nitrogen double bond with the nitrogen atom connected to an aryl or alkyl group  charged Mechanism of transamination:

24 Sulfur compounds Structurally similar to oxygen compound

25 Thiols: R-SH (sulfhydryl group) Properties:  Not form hydrogen bonds  Stronger acids than alcohols  Easily oxidized → disulfide Examples: Cystein

26 Disulfides: R-S-S-R Disulfide-bonded cystein residues  The disulfide bond forms when the two thiol groups are oxidized (reverse reaction)  Protein conformation!

27 Glutathione  An antioxidant (elimination of H 2 O 2 and organic hydroperoxides) Gly Cys Glu Gly Cys Glu Gly Cys SH Glu S Oxidized form of glutathione (dimer, disulphide) Reduced form of glutathione (monomer) Glutathione peroxidase Glutathione reductase + R-O-O-H + H 2 O + NADPH

28 Examples: Methionine S-Adenosylmethionine (SAM) = sulfonium ion  Highly reactive methyl group (an important methylation agent)! Sulfides: R-S-R

29 Sulfonic acids: R-SO 3 H Examples: Taurin = derivate from cysteine Sulfonamides  important chemoterapeutics

30 Nitrogen compounds: 1. Amines  neurotransmitters (GABA, dopamine, serotonine, catecholamines, acetylcholine)  amino acids  alkaloids (cocaine, opiates) 2. Amides  peptide bond  urea  creatine 3. Imines  Schiff bases Sulfur compounds 1. Thiols - disulfide  glutathione, proteins 2. Sulfides  S-adenosylmethionine 3. Sulfonic acid  Taurin Summary

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