Презентация Factors affecting the rate of chemical reaction онлайн

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Содержание слайда: Factors affecting the rate of chemical reaction The chemical reaction rate depends on: The nature of reacting substances: Н2 + F2 → 2HF (in the dark, in cold with the explosion) Н2 + Cl2 2HCl (in the light) H2 + I2 2HI (the reaction is reversible)

Содержание слайда: Factors affecting the rate of chemical reaction The chemical reaction rate depends on: 2. The state of the reacting substances. 3. Environment the reaction is proceeding in. 4. The external conditions. 5. Concentration.

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Содержание слайда: Catalytic reactions Catalysis is the process of changing the rate of reaction by catalysts. Reactions taking place with the participation of catalysts called catalytic. A catalyst is a substance that changes the rate of a chemical reaction, but it is not spent. Catalysis has specificity:

Содержание слайда: Enzymes Enzymes are protein molecules able to accelerate the course of biochemical reactions. Other than enzymes-proteins there are so-called ribozymes - RNA capable of catalysis.

Содержание слайда: The active center is a plot of an enzyme which is binding, and the transformation of molecules of substrate. The active center is a plot of an enzyme which is binding, and the transformation of molecules of substrate. E - enzyme P - product S – substrate I - inhibitor [ES] – enzyme-substrate complex [EP] – enzyme-product complex

Содержание слайда: Factors affecting the activity of the enzyme The concentration of the substrate. In 1913 Michaelis and Menten proposed equation = max[S]/Km+[S] Km - Michaelis constant. A limiting factor of the reaction is the formation of the enzyme-substrate complex. Km= the substrate concentration at which the reaction rate equals to half of the rate to the maximum.

Содержание слайда: Specificity of enzymes: highly specific; law specific; nonspecific. Most of the enzymes are highly specific, since they change only 1 substrate. Low specific interact with a group of related substances. Nonspecific change substances of different groups.

Содержание слайда: The mechanism of action of enzymes Classic catalysts operate due to the energy of activation. Catalysts do not change  G they reduce the activation energy. The decrease of activation energy increases the number of molecules able to overcome the energy barrier.

Содержание слайда: The principle of irreversibility of chemical reactions Irreversible reactions lead: to the formation of gaseous substances: Zn + 2H2SO4 (k) → ZnSO4 + SO2 ↑+ 2H2O sedimentation: Ba(NO3)2 + Na2SO4 → BaSO4 ↓+ 2NaNO3 weak electrolyte: Na2S + 2HCl → 2NaCl + H2S (in solution)

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Содержание слайда: The decrease of activation energy is achieved by: 1. Orientation substrates. 2. Theory of steric interactions. Fischer suggested that the active center of spatially corresponds to the substrate molecule. Due to its spatial specificity of an enzyme and the substrate are oriented specifically.

Содержание слайда: 3. The theory of induced correspondence. Suggested by Koshland. After the formation of the enzyme-substrate complex, inside the enzyme molecule some conformation changes can be observed. They induce corresponding changes in the substrate molecule.

Содержание слайда: 4. the formation of intermediate complexes. 4. the formation of intermediate complexes. а) the acid-basic catalysis. In the enzyme donors protons can be cysteine amino acid residues, glutamate, aspartate, lysine, gistidine. Acceptors of protons are the same groups but in the deprotonated form. b) covalent catalysis. During it the substrate or part of it formes stable covalent bonds with the enzyme molecule. c) nucleophilic-electrophilic attack

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Содержание слайда: Mechanisms of chemical reactions Atoms, molecules, radicals, or ions may participate in reaction. It’s simple, ion, and radical reaction. Reactions occurring between the molecules are called simple : H2 + I2=2HI 2NO + Cl2=2NOCl Activation energy is 150-450 kJ/mol.

Содержание слайда: Mechanisms of chemical reactions Chain reactions. Radical reactions proceed by a chain mechanism. Their peculiarity lies in the fact that a primary activation leads act to transform a huge number of molecules in the raw materials radicals. For example, the reaction H2 + Cl2=2HCl proceeds by a radical chain mechanism by heating or by lighting light. Due to the absorption of a photon (h) Cl2 molecule dissociates into free radicals - chlorine atoms: Сl2 + h =Сl + * Сl Atom radical Cl * then reacts with the hydrogen molecule, forming a molecule of HCl and atom radical * N. Last interacts with a molecule of Cl2, HCl and atom forms a radical Cl *, etc. *Сl + Н2=НСl + *Н *Н + Сl2= НСl + *Сl and etc. On each absorbed quantum of light there is formed up to 100,000 molecules НСl