Unsolved problems in chemistry tend to be questions of the kind "Can we make X chemical compound?", "Can we analyse it?", "Can we purify it?" and are commonly solved rather quickly, but may just as well require considerable efforts to be solved. However, there are also some questions with deeper implications. This article tends to deal with the areas that are the center of new scientific research in chemistry. Problems in chemistry are considered unsolved when an expert in the field considers it unsolved or when several experts in the field disagree about a solution to a problem .
Organic chemistry problems
* Solvolysis of the norbornyl cation: Why is the norbornyl cation so stable? Is it symmetrical? if so why? This problem has been largely settled for the unsubstituted norbornyl cation, but not for the substituted cation. See Non-classical ion.
* On water reactions: Why are some organic reactions accelerated at the water-organic interface? See On water reactions.
* What is the origin of the bond rotation barrier in ethane, steric hindrance or hyperconjugation? See Bond rotation barrier.
* What is the origin of the alpha effect? Nucleophiles with an electronegative atom and one or more lone pairs adjacent to the nucleophilic center are particularly reactive. See: Alpha effect.
* Better-than perfect enzymes: Why do some enzymes exhibit faster-than-diffusion kinetics? See Enzyme kinetics.
* What is the origin of homochirality in amino acids and sugars? See Homochirality.
* Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions?  See Protein folding.
* What are the chemical origins of life? How did non-living chemical compounds generate self-replicating, complex life forms? See Abiogenesis.
Physical chemistry problems
* What is the electronic structure of the high temperature superconductors at various points on the phase diagram? Can the transition temperature be brought up to room temperature? See Superconductor.
* Feynmanium: What are the chemical consequences of having an element, with an atomic number above 137, whose 1s electrons must travel faster than the speed of light? Is "Feynmanium" the last chemical element that can physically exist? The problem may actually occur at approximately Element 137, given the finite extension of nuclear-charge distribution. See the article on Extension of the periodic table beyond the seventh period and section Relativistic effects of Atomic orbital.
* How can electromagnetic energy (photons) be efficiently converted to chemical energy? (E.g. splitting of water to hydrogen and oxygen using solar energy.)
* What is the nature of bonding in hypervalent molecules? See Hypervalent molecules.
* What is the structure of water? According to Science Magazine in 2005, one of the 100 outstanding unsolved problems in science revolves around the question of how water forms hydrogen bonds with its neighbors in bulk water. See: water cluster
1. ^ For relevant citations also see the satellite pages
2. ^ Unique Reactivity of Organic Compounds in Aqueous Suspension Sridhar Narayan, John Muldoon, M. G. Finn, Valery V. Fokin, Hartmuth C. Kolb, K. Barry Sharpless Angew. Chem. Int. Ed. 21/2005 p 3157 ,
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4. ^ a b c "So much more to know". Science 309 (5731): 78–102. July 2005. doi:10.1126/science.309.5731.78b. PMID 15994524. http://www.sciencemag.org/cgi/content/full/309/5731/78b.
5. ^ MIT OpenCourseWare 7.88J / 5.48J / 7.24J / 10.543J Protein Folding Problem, Fall 2003 Lecture Notes - 1, 2003, http://ocw.mit.edu/NR/rdonlyres/Biology/7-88JProtein-Folding-ProblemFall2003/2E446AD3-5702-49F1-9B95-9DC298E2ACB3/0/lec01.pdf
6. ^ Duffie, John A. (2006). Solar Engineering of Thermal Processes. Wiley-Interscience. p. 928. ISBN 978-0471698678.
7. ^ Brabec, Christoph; Vladimir Dyakonov, Jürgen Parisi, Niyazi Serdar Sariciftci (2006). Organic Photovoltaics: Concepts and Realization. Springer. p. 300. ISBN 978-3540004059.