По поводу теории по подбору катализаторов, если отвечать коротко, то теория называется "методом тыка".
Now I am switching to English, since it is easier that way. Question 1: Most of the catalysts used today in synthetic organic chemistry are metal based. That means there is a metal with some ligands attached to it that dictate its electronic properties and geometry. For the metal to be used as a catalyst it has to satisfy at least one of the two following conditions, and sometimes both are necessary. First of all the metal has to have an open coordination site for the substrate to attach to it. To put in simple terms the metal has to have a guest room iн the house, and that means free molecular orbitals. That is why many of the catalyst that we have today are made with transition metals, such as ruthenium and palladium. The other condition is the ability to exist in multilple oxidation states and it is the shutelling of the metal between the oxidation states that is one of the driving forces of the reaction.
There is a relatively new field in the catalytic chemistry which is looking at utilizing non-metal catalyst. For example, proline is a very common non-metal catalyst. A lot of times people are looking at short peptides to be used as the catalysts. Which brings us to you second question. Technically, the enzymes can be used as a catalysts in organic reaction, but the problem is that most of the organic reactions do not work in water, but work in non-polar organic solvents. Now, some enzymes can function in non-polar environment, but many can not, and as far as I know it is difficult to predict. However, if you have an organic reaction that works in water then enzyme would be a catalyst of choice, since it is environmentally benign as opposed to a metal catalyst. And of course, the pharmaceutical company would love this kind of reaction because it will keep FDA very very happy.
A lot of times enzymes can serve as a model for catalyst design. If you know the active site of an enzyme you can design a catalyst that would contain the structural motive but overall would be a much smaller molecule. That is why you see short peptides being used as catalysts so often.
With regard to question 3. Any chemist will tell you that the reason why catalase is more effective than platinum in this regard is because it more effectively lowers the transition state of the reaction, but why is catalase in turn more effective in this instance noone truly knows. There are some theories, but basically its like asking why 2x2=4. That's just the way it is.
Question 4: the short answer is no, there is no such theory. Predictions are still hard to do in chemistry, the best you can do is an educated guess.
Question 5: as far as reading goes the best journals for non-professionals to my knowledge are Science and Nature. Things that are described there usually have significant impact on the society in general, rather than just on scientific community, and the description is more general and more user friendly. You can also ask me and I'll try to help you to the best of my knowledge:).
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timeasmymeasure
Re: Только если/когда будет время/желание
Date: 2004-08-02 11:39 am (UTC)Now I am switching to English, since it is easier that way. Question 1: Most of the catalysts used today in synthetic organic chemistry are metal based. That means there is a metal with some ligands attached to it that dictate its electronic properties and geometry. For the metal to be used as a catalyst it has to satisfy at least one of the two following conditions, and sometimes both are necessary. First of all the metal has to have an open coordination site for the substrate to attach to it. To put in simple terms the metal has to have a guest room iн the house, and that means free molecular orbitals. That is why many of the catalyst that we have today are made with transition metals, such as ruthenium and palladium. The other condition is the ability to exist in multilple oxidation states and it is the shutelling of the metal between the oxidation states that is one of the driving forces of the reaction.
There is a relatively new field in the catalytic chemistry which is looking at utilizing non-metal catalyst. For example, proline is a very common non-metal catalyst. A lot of times people are looking at short peptides to be used as the catalysts. Which brings us to you second question. Technically, the enzymes can be used as a catalysts in organic reaction, but the problem is that most of the organic reactions do not work in water, but work in non-polar organic solvents. Now, some enzymes can function in non-polar environment, but many can not, and as far as I know it is difficult to predict. However, if you have an organic reaction that works in water then enzyme would be a catalyst of choice, since it is environmentally benign as opposed to a metal catalyst. And of course, the pharmaceutical company would love this kind of reaction because it will keep FDA very very happy.
A lot of times enzymes can serve as a model for catalyst design. If you know the active site of an enzyme you can design a catalyst that would contain the structural motive but overall would be a much smaller molecule. That is why you see short peptides being used as catalysts so often.
With regard to question 3. Any chemist will tell you that the reason why catalase is more effective than platinum in this regard is because it more effectively lowers the transition state of the reaction, but why is catalase in turn more effective in this instance noone truly knows. There are some theories, but basically its like asking why 2x2=4. That's just the way it is.
Question 4: the short answer is no, there is no such theory. Predictions are still hard to do in chemistry, the best you can do is an educated guess.
Question 5: as far as reading goes the best journals for non-professionals to my knowledge are Science and Nature. Things that are described there usually have significant impact on the society in general, rather than just on scientific community, and the description is more general and more user friendly. You can also ask me and I'll try to help you to the best of my knowledge:).
Надеюсь, я тебя не совсем запутала.