Reaction mechanism Mgr. Renata Köhlerová, PhD. Support for seminar Reaction mechanism Mgr. Renata Köhlerová, PhD.

Choose the correct contention(s) about nucleophilic agents: Task 1 Choose the correct contention(s) about nucleophilic agents: They have affinity for reactants with positive charge. They belong to positively charged ions. Example of them is molecule of water. They originate by homolytic bond cleavage. Answer Explanation Back End

Napište všechny izomery sloučeny C6H12. Answer 1 Napište všechny izomery sloučeny C6H12. Choose the correct contention(s) about nucleophilic agents: A. They have affinity for reactants with positive charge. B. They belong to positively charged ions. C. Example of them is molecule of water. D. They originate by homolytic bond cleavage. bla bla Next Explanation Back End

Agents Explanation 1 Answer The mechanism of the reaction is determined by particles called agents in organic chemistry and biochemistry. Agents frequently arise by cleavage of the molecule into two parts. If a non-polar covalent bond is cleavaged symmetricaly, they are produced two particles with an unpaired electron - radicals. It is a homolytic cleavage. A polar covalent bond is cleavaged asymmetricaly. The atom with the higher electronegativity obtains both bonding electrons and the atom the lower electronegativity will have place in valence orbital. It is a heterolytic cleavage. Such they arise carbocations and carbanions. Nucleophilic agents arise by heterolytic cleavage. They have non-bonding electron pairs or contain p electrons.They often are anions. For example molecular: H2O, NH3 and ionic: OH-, NH2-, Cl-, I-, CN- Electrophilic agents arise by heterolytic cleavage, too. They have incomplete valence octet and have full or partial positive charge. For example molecular: HCl, H2SO4, AlCl3 and ionic: H3O+, NH4+, N02+, Br+, CH3+ Answer Back End

What is the mechanism halogenation of ethene of benzene of ethane Task 2 What is the mechanism halogenation of ethene of benzene of ethane of buta-1,3-diene? Answer Explanation Back End

What is the mechanism halogenation of ethene of benzene of ethane Answer 2 What is the mechanism halogenation of ethene of benzene of ethane of buta-1,3-diene? CH3-C-H O CH2=CH OH electrophilic adition electrophilic substitution radical substitution Next Explanation Back End

Chemical reaction Explanation 2 Answer Chemical transformations are not random events, but they have the exact causes case inner structure of the reactants. It is characterized for chemical reactions, that some bonds are destroyed and others are arised. The journey from reactants to products usually comes through many intermediates, which - if they exists only a very short period of time – we called activated complexes. The reaction mechanism is a detailed description of all the particular changes at the molecular level during the reaction. It is important for understanding chemical processes. We use the terms substrate and agent instead of reactants in biochemistry. We use chemical equations to write the chemical reactions in iorganic chemistry and reaction schemes in organic chemistry. Schemes show only qualitative, not quantitative changes. The reaction can be split according to many aspects. The most common division is substitution, addition, elimination and rearrangement of organic chemistry. continue Answer Back End

Chemical reaction - continue Explanation 2 Chemical reaction - continue Substitution Atom or group of atoms in the carbon chain are exchanged with another atom / group. The most exchanged atom is hydrogen. It is typical for saturated hydrocarbons and arenes. Adition The saturated bond is created from unsaturated (C=C , C=O) bond. unsaturated hydrocarbons, oxoderivatives Elimination The small particule is cleavaged from molecule (H2, H2O, NH3, HX, X2 …) and double bond is created. Rearrangement intramolecular substitution (fe. keto – enol) continue Answer Back End

Chemical reaction – continue: Substitution Explanation 2 Chemical reaction – continue: Substitution Type of reaction Example of substrates Reaction radical alkanes halogenation burning (oxidation) electrophilic arenes nitration sulfonation nucleophilic halogen derivatives hydroxy compounds Answer Back continue End

Chemical reaction – continue: Adition Explanation 2 Chemical reaction – continue: Adition Type of reaction Example of substrates Reaction radical arenes hydrogenation electrophilic alkenes alkynes halogenation nucleophilic oxo compounds creating of hemiacetals Answer Back End

Substitutional reactions are typical for A) benzene B) oktane Názvosloví Task 3 Substitutional reactions are typical for A) benzene B) oktane C) cyklohexene D) ethyne Answer Explanation Back End

Substitutional reactions are typical for A) benzene B) oktane Answer 3 Substitutional reactions are typical for A) benzene B) oktane C) cyklohexene D) ethyne Next Explanation Back End

Substitution Explanation 3 Type of reaction Example of substrates Atom or group of atoms in the carbon chain are exchanged with another atom / group. The most exchanged atom is hydrogen. It is typical for saturated hydrocarbons and arenes. Type of reaction Example of substrates Reaction radical alkanes halogenation burning (oxidation) electrophilic arenes nitration sulfonation nucleophilic halogen derivatives hydroxy compounds Answer Back End

The typical mechanism of chloration of butane is electrophilic adition Názvosloví Task 4 The typical mechanism of chloration of butane is electrophilic adition radical substitution C) nucleophilic substitution D) radicaladition Answer Explanation Back End

The typical mechanism of chloration of butane is electrophilic adition Answer 4 The typical mechanism of chloration of butane is electrophilic adition radical substitution C) nucleophilic substitution D) radicaladition Next Explanation Back End

Cl* + CH4  HCl + H3C* Radical substitution – chloration of methane Explanation 4 Radical substitution – chloration of methane Iniciation (origin of radicals) Cl2  2 Cl* Propagation Cl* + CH4  HCl + H3C* H3C* + Cl2  CH3Cl + Cl* Termination 2 Cl*  Cl2 Cl* + H3C*  CH3Cl H3C* + H3C*  CH3CH3 Answer Back End

A) ES requires attacking agent wiht a positive charge. Názvosloví Task 5 Choose the correct contention(s) about electrophilic substitution (ES): A) ES requires attacking agent wiht a positive charge. B) ES requires attacking agent wiht a negative charge. C) We need Br+ + for the bromination of benzene. We need Br- for the bromination of benzene. Answer Explanation Back End

A) ES requires attacking agent wiht a positive charge. Answer 5 Choose the correct contention(s) about electrophilic substitution (ES): A) ES requires attacking agent wiht a positive charge. B) ES requires attacking agent wiht a negative charge. C) We need Br+ for the bromination of benzene. We need Br- for the bromination of benzene. Next Explanation Back End

Electrophilic substitution Explanation 5 Electrophilic substitution It is very common reaction of arenes. At first electrophilic particle reacts with -electron of aromatic system and creates  complex. At second it is rearranged on  complex, there is an electrophilic particle bonded to a certain atom and the compound temporarily loses its aromatic character. Then the proton is separated and aromatic character is restored. It is a typical mechanism for nitration, sulfonation and chlorination. H2O + +NO2 H-O-NO2 + H-O-SO2-O-H -> H-O-NO2+ -O-SO2-O-H H nitronion cation nitration mixure Answer NO2 + H-O-SO2-O-H H + +NO2 ----> H +NO2 ----> H NO2 -----> -O-SO2-O-H Back π complex σ complex End

A) The first reaction is nucleophilic addition. Názvosloví Task 6 Reaction of two molecules of ethanal in the presence of a suitable catalyst is an example of two-step reaction: A) The first reaction is nucleophilic addition. B) The attacking particule has a positive charge. C) The second reaction is dehydration. D) The product is 2-butenal. Answer Explanation Back End

A) The first reaction is nucleophilic addition. Answer 6 Reaction of two molecules of ethanal in the presence of a suitable catalyst is an example of two-step reaction: A) The first reaction is nucleophilic addition. B) The attacking particule has a positive charge. C) The second reaction is dehydration. D) The product is 2-butenal. Next Explanation Back End

Condensation Explanation 6 It is a very common type of reaction in organic chemistry. Basically there are two subsequent reactions - addition and elimination. We talk about aldol condensation in the case of aldehydes. Answer Back End

The condensation reaction is: addition with the consequent elimination Názvosloví Task 7 The condensation reaction is: addition with the consequent elimination formation of polyvinyl chloride reaction of two molecules of ethanol to give diethyl ether reaction of two molecules of acetaldehyde Answer Explanation Back End

The condensation reaction is: addition with the consequent elimination Answer 7 The condensation reaction is: addition with the consequent elimination formation of polyvinyl chloride reaction of two molecules of ethanol to give diethyl ether reaction of two molecules of acetaldehyde Next Explanation Back End

Condensation Explanation 7 It is a very common type of reaction in organic chemistry. Basically there are two subsequent reactions - addition and elimination. We talk about aldol condensation in the case of aldehydes. Answer Back End

Markovnikovo rule is applied in the reaction molecule of HCl with Názvosloví Task 8 Markovnikovo rule is applied in the reaction molecule of HCl with A) 2-butene B) 1-butene C) cyklohexene D) ethene E) propenoic acid Write formulas and name products of these reactions. Answer Explanation Back End

Markovnikovo rule is applied in the reaction molecule of HCl with Answer 8 Markovnikovo rule is applied in the reaction molecule of HCl with A) 2-butene B) 1-butene C) cyklohexene D) ethene E) propenoic acid Write formulas and name products of these reactions. 2-chlorobutane chloorcyklohexane chloroethane 2-chloropropanoic acid Next Cl Explanation Back CH3-CH2Cl CH3-CH-COOH Cl End

Hydrogen bonds to the carbon, which has more hydrogens. Explanation 8 Markovnikov´s rule The most electronegative part of the attached molecule is bonded to the carbon which carries fewer hydrogens. or Hydrogen bonds to the carbon, which has more hydrogens. Answer CH2=CH-CH3 + HCl --> CH3-CH-CH3 Cl Back End

A) leads to a loss of hydrogen. B) belongs to the oxidative reactions. Názvosloví Task 9 Dehydratation A) leads to a loss of hydrogen. B) belongs to the oxidative reactions. C) usually leads to the formation of a double bond. D) belongs to the reductive reactions. Answer Explanation Back End

A) leads to a loss of hydrogen. B) belongs to the oxidative reactions. Answer 9 Dehydratation A) leads to a loss of hydrogen. B) belongs to the oxidative reactions. C) usually leads to the formation of a double bond. D) belongs to the reductive reactions. Next Explanation Back End

Reactions in v biochemistry Explanation 9 Reactions in v biochemistry Additions and eliminations are common reactions in living organisms. They are basically opposite processes. A low molecular weight compound binds to the multiple bond in addition, thus contrary a double bond is formed and a small part is separated in elimination. If that compound is hydrogen, we can talk about hydrogenation (reduction) in the case of addition and dehydrogenation (oxidation) for elimination. continue +2H -2H CH3CHO CH3CH2OH Answer Back End

Reactions in v biochemistry Explanation 9 Reactions in v biochemistry Hydratation Dehydratation Carboxylation Decarboxylation Amination Deamination +H2O -H2O CH2=CH-COOH CH3CHCOOH OH +CO2 -CO2 CH3 -CO~CoA HOOC-CH2-CO~CoA Answer NH2 CH=CH-COOH CH2-CH-COOH N H Back +NH3 -NH3 End

Creating of 2-butanone from secondary butanol is A) reduction Názvosloví Task 10 Creating of 2-butanone from secondary butanol is A) reduction B) hydrogenation C) oxidation D) dehydration E) dehydrogenation Answer Explanation Back End

Creating of 2-butanone from secondary butanol is A) reduction Answer 10 Creating of 2-butanone from secondary butanol is A) reduction B) hydrogenation C) oxidation D) dehydration E) dehydrogenation Next Explanation Back End

Hydrogenation Dehydrogenation Explanation 10 Reactions in v biochemistry Additions and eliminations are common reactions in living organisms. They are basically opposite processes. A low molecular weight compound binds to the multiple bond in addition, thus contrary a double bond is formed and a small part is separated in elimination. If that compound is hydrogen, we can talk about hydrogenation (reduction) in the case of addition and dehydrogenation (oxidation) for elimination. continue +2H -2H CH3CHO CH3CH2OH Answer Hydrogenation Dehydrogenation Back End

Reactions in v biochemistry Explanation 10 Reactions in v biochemistry Hydratation Dehydratation Carboxylation Decarboxylation Amination Deamination +H2O -H2O CH2=CH-COOH CH3CHCOOH OH +CO2 -CO2 CH3 -CO~CoA HOOC-CH2-CO~CoA Answer NH2 CH=CH-COOH CH2-CH-COOH N H Back +NH3 -NH3 End

A) positive inductive effect of chlorine. Názvosloví Task 11 The fact that trichloroacetic acid is a stronger acid than acetic acid can be explained by A) positive inductive effect of chlorine. B) positive mesomeric effect of chlorine. C) negative inductive effect of chlorine. D) negative mesomeric effect of chlorine. Answer Explanation Back End

A) positive inductive effect of chlorine. Answer 11 The fact that trichloroacetic acid is a stronger acid than acetic acid can be explained by A) positive inductive effect of chlorine. B) positive mesomeric effect of chlorine. C) negative inductive effect of chlorine. D) negative mesomeric effect of chlorine. Next Explanation Back End

-X -NO2 -CO -CN -COOR -COOH -COR -SO3H Explanation 11 Effects Inductive and mesomeric effect A shift of electric charge is a result of its compensation in some derivatives of hydrocarbon. If  electrons move to one atom, we talk about induction effect (I effect). If  electrons move, it is a mesomeric effect (M-effect). If is direction of moving of electric charge to a heteroatom, we talk about the negative (-) effect. If is direction of moving of electric charge to a hydrocarbon, we talk about the positive (+) effect. Answer   I-effect M-effect + Mg Li -R -X -NH2 - -X -NO2 -CO -CN -COOR -COOH -COR -SO3H -NO2 -CO -CN -COOR -COOH Back End

Názvosloví Task 12 Do we find any organic compound (aliphatic or aromatic) which is bonded one of the halide elements in the organism? Answer Back End

Only one type –thyroid hormones with iodine Answer 12 Do we find any organic compound (aliphatic or aromatic) which is bonded one of the halide elements in the organism? Only one type –thyroid hormones with iodine Next Back End

Assign to that type of reaction one of the following answers: Názvosloví Task 13 Assign to that type of reaction one of the following answers: hydration electrophilic substitution decarboxylation condensation during β-oxidation of fatty acids in the formation of citric acid; in the pentose cycle iodination of tyrosine to form thyroid hormone in the formation of biogenic amines from amino acids Answer Back End

Assign to that type of reaction one of the following answers: hydration electrophilic substitution decarboxylation condensation 1A, 2D, 3B, 4C during β-oxidation of fatty acids in the formation of citric acid; in the pentose cycle iodination of tyrosine to form thyroid hormone in the formation of biogenic amines from amino acids Next Back End

Homolytic cleavage of bond leads to the formation of radicals. Názvosloví Task 14 Homolytic cleavage of bond leads to the formation of radicals. can be induced by UV radiation. leads to the formation of highly reactive residue. proceeds in with alkenes in the presence of benzoyl peroxide Answer Explanation Back End

Homolytic cleavage of bond leads to the formation of radicals. Answer 14 Homolytic cleavage of bond leads to the formation of radicals. can be induced by UV radiation. leads to the formation of highly reactive residue. proceeds in with alkenes in the presence of benzoyl peroxide Next Explanation Back End

Homolytic cleavege Explation 14 A symmetrical cleavage of non-polar covalent bond and production of two particles with an unpaired electron - radicals.are typical manifestation of homolytic ceavage. Homolytic agents usually attack the non-polar covalent bonds. Answer Back End

Which reaction we can marked as reduction? Názvosloví Task 15 Which reaction we can marked as reduction? fat hardening (hydrogenation) creating of fumarate from succinate creating of enolpyruvate from pyruvate creating of haemiglobin from haemoglobin Answer Back End

Which reaction we can marked as reduction? Answer 15 Which reaction we can marked as reduction? fat hardening (hydrogenation) creating of fumarate from succinate creating of enolpyruvate from pyruvate creating of haemiglobin from haemoglobin Hydrogenation is binding of hydrogen to unsaturated compounds - an example of reduction. It is dehydrogenation - example oxidation reaction. This is not a redox reaction, but the rearrangement (tautomerism). It is the loss of electron from Fe2+ and its oxidation to Fe3+. Next Back End

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