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Can you name examples of reactions that are endothermic and simple molecules are combined into more complex ones at the same time? Like what plants do they take heat and sunlight and they synthetize air and water into organic fuels such as glucose and ethanol. I found similar experiments made for carbon capture some call it reverse combustion, they take air and water, and with help of heat or electricity they turn it into the ethanol or glucose. So can you name similar reactions, where something similar happens? I really can’t find an answer anywhere. Please help . Thank you for taking your time to read this.

AverageJoe
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    Is there a serious reason for not writing chemical formulas properly ? – Poutnik Jan 28 '21 at 17:48
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    What are you really looking for ? In the beginning, you are looking for the "synthesis of $\ce{CO2 + H2O}$". Well ! this operation is carried out every day in the combustion of any fuel like gasoline, oil, petroleum, alcohol, wood, etc. It is not a synthesis and it is not endothermic. In your second sentence, you speak of a company that makes vodka out of air and water. This is non-sense, for lack of Carbon atoms. In your third sentence you speak of the synthesis of glucose out of CO2 in the lab. No labs are able to do it. Only plants can do it. I repeat : What are you looking for ? – Maurice Jan 28 '21 at 18:06
  • Its not non-sense, look at this for example https://phys.org/news/2017-09-alcohol-thin-air.html – AverageJoe Jan 28 '21 at 18:15
  • Also synthetis is different from combustion – AverageJoe Jan 28 '21 at 18:25
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    "There is never time to write questions properly, but there is always much more time for their explanation." – Poutnik Jan 28 '21 at 19:17
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    I thought this platform is for unexperienced person to ask a question and get answer from someone experienced. Like that’s the whole point of asking questions. So in order to get anyone to at least try to answer my question it has to be perfect? Like how do I write perfect question if I don’t speak “professional chemist” or “experienced entitled stack exchange user” language? – AverageJoe Jan 28 '21 at 19:40
  • Do kids ask perfect questions? Would you act like this if your kid asked something? – AverageJoe Jan 28 '21 at 20:13
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    Apparently you have entirely rewritten your question. Now you are looking for examples of reaction producing organic compounds out of CO2 and H2O. Well you can name all the reactions carried out by plants, like the synthesis of cellulose, of starch, of sugars, of oils, of proteins, of acids like citric acid or ascorbic acids, of dyes like carotene, of perfumes like menthol, thymol, limonene, etc. Well I stop this list here. These substances are made by plants without heating, without distilling, and in aqueous solution. Presently chemists are not able to synthesize them under these conditions. – Maurice Jan 28 '21 at 21:03
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    I think this question should not have been close or it might be reopened. OP should clarify if s/he put special emphasis in the word synthesis. If it is meant for reaction, then the answer is to look for the Free Energy of the process. If it is meant for a reaction organising matter and placing energy into it (at least one part of the system sees lowering of entropy), it becomes the topic of why reactions within the living kingdom are special. Not that I know the answer or I can debate it with lucidity, but the issue is interesting and opens, like in the photosynthesis chemistry community. – Alchimista Jan 29 '21 at 09:35
  • @Alchimista thank you for your comment. Could you please help me rephrasimg the question to make it better? When I researched word synthetis, I understood that it is combining smaller, simpler molecules into more complex ones. Thats where I am coming from. So I wanted to know about more processes where more complex molecules are formed and at the same time chemical reaction takes hear or energy from the environment. Also I think it is interesting topic and even more important nowadays because of environmental problems – AverageJoe Jan 29 '21 at 14:51
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    You are right that synthesis can be taken as to build up complex things from smaller. Perhaps it was even the original meaning. However synthesis can be read as whatever reaction is conducted. So dismantling a complicated molecule into pieces of interest can be called somehow the synthesis of the latter. This said, on the light of your question as for the latter comment, I am afraid only living organisms do that. There is a question that I can't find right now, here on in physics SE, to which I have contributed full of wish but I am crystal saying that at the end the issue isn't that clear. – Alchimista Jan 29 '21 at 15:03
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    .... clear to me. If I have understood correctly what are you referring to, it is indeed a difficult thermodynamics issue linked to the origin, or at least the prerogatives, of life. Try to look for that thread. Same I'll do. – Alchimista Jan 29 '21 at 15:07
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    Related. If you are not concerned with the entropic aspect then forget the link and look for spontaneous reaction - free energy. Decreasing of Free Energy gives you the criterion for spontaneous reaction at given conditions. https://physics.stackexchange.com/questions/453853/is-it-true-that-only-living-things-and-man-made-objects-can-make-an-endothermic/454208#454208 – Alchimista Jan 29 '21 at 15:33
  • @Alchimista oh that explains a lot and nicely connect to this topic. Just another proof for me that chemistry, biology or physics - all of these don’t exist in vacuum. It’s just how people categorised the nature and it’s processes. But everything is connected and sometimes we need to see bigger picture to understand things better. – AverageJoe Jan 29 '21 at 16:15

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Here are three examples of endothermic synthesis reactions. Heats of formation are given at 1 bar, 298.15 K. The first of these, the production of ozone, is naturally-occurring.

$$ \begin{align} \ce{3/2 O2(g) &-> O3(g)} &\quad \Delta_\mathrm{f}H^\circ &= \pu{142 kJ mol^-1}\\ \ce{N2(g) + 1/2 O2(g) &-> N2O(g)} &\quad \Delta_\mathrm{f}H^\circ &= \pu{82 kJ mol^-1}\\ \ce{1/2 N2(g) + O2(g) &-> NO2(g)}&\quad \Delta_\mathrm{f}H^\circ &= \pu{33 kJ mol^-1} \end{align} $$

andselisk
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theorist
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  • Does this classic example count? – Ed V Jan 29 '21 at 13:29
  • @EdV and this one: https://chemistry.stackexchange.com/questions/86855/the-coldest-the-most-endothermic-reaction – Nilay Ghosh Jan 29 '21 at 13:35
  • @NilayGhosh Yes! And I was kind of hoping that entropy and free energy could get an oblique nod (nothing more than that: simply name-checking them), just to indicate that enthalpies, while cool characters here, are not the entire cast of the play! – Ed V Jan 29 '21 at 13:58
  • @theorist thank you very much for the answer. But after some research I found out that both n2o and no2 are naturally occurring too. – AverageJoe Jan 29 '21 at 15:32
  • https://chemistry.stackexchange.com/questions/101691/why-does-ozone-have-higher-entropy-than-oxygen – Alchimista Jan 29 '21 at 15:48
  • @EdV I don't think so, since that seems to be a replacement reaction rather than a synthesis reaction. – theorist Jan 30 '21 at 02:11
  • @Joe839949 Yes, those compounds are naturally-occurring, but I don't know if those reactions are. E.g., most NO2 in the atmosphere is not made combining N2 and O2, but rather by the burning of nitrogen-containing fuels. And that is not an endothermic process. – theorist Jan 30 '21 at 02:20
  • I guess I take a pedestrian view of synthesis. For example, I used to synthesize white fuming nitric acid (in my basement chemistry lab when I was in high school) by reacting concentrated sulfuric acid with strontium nitrate. I used a retort and heat. So I got the WFNA and strontium sulfate was the byproduct. But I take your point! – Ed V Jan 30 '21 at 02:24