Intermolecular force: Difference between revisions

or repulsion]] which act between atoms and other types of neighbouring particles, e.g. [[atom]]s or [[ion]]s. Intermolecular forces are weak relative to [[intramolecular force]]s – the forces which hold a molecule together. For example, the [[covalent bond]], involving sharing electron pairs between atoms, is much stronger than the forces present between neighboring molecules <ref>{{Cite journal |last1=Fischer |first1=Johann |last2=Wendland |first2=Martin |date=October 2023 |title=On the history of key empirical intermolecular potentials |url=https://linkinghub.elsevier.com/retrieve/pii/S0378381223001565 |journal=Fluid Phase Equilibria |language=en |volume=573 |pages=113876 |doi=10.1016/j.fluid.2023.113876|bibcode=2023FlPEq.57313876F |doi-access=free }}</ref>. Both sets of forces are essential parts of [[Force field (chemistry)|force fields]] frequently used in [[molecular mechanics]].

*[[Cation–π interaction|Cation–π]], σ–π and π–π bonding

In the broadest sense, it can be understood as such interactions between any particles ([[molecule]]<nowiki/>s, [[atom]]<nowiki/>s, [[ion]]<nowiki/>s and [[molecular ion]]<nowiki/>s) in which the formation of chemical, that is, ionic, covalent or metallic bonds does not occur. In other words, these interactions are significantly weaker than [[Covalent bond|covalent]] ones and do not lead to a significant restructuring of the [[electronic structure]] of the interacting particles. (It should be noted that the aboveThis is only partially true. For example, all [[Enzyme|enzymatic]] and [[Catalysis|catalytic reactionreactions]]<nowiki/>s begin with a weak intermolecular interaction between a substrate and an [[enzyme]] or a molecule with a [[Catalyst: Agents of Change|catalyst]], but several such weak interactions with the required spatial configuration of the active center of the enzyme lead to significant restructuring changes the energy state of molecules or substrate, which ultimately leads to the breaking of some and the formation of other covalent chemical bonds. Strictly speaking, all [[Enzyme catalysis|enzymatic reactionreactions]]<nowiki/>s begin with intermolecular interactions between the [[Substrate (chemistry)|substrate]] and the enzyme, therefore the importance of these interactions is especially great in [[biochemistry]] and [[molecular biology]] ,<ref>{{Cite web |title=Biochemistry and Molecular Biology - Paperback - Despo Papachristodoulou, Alison Snape, William H. Elliott, Daphne C. Elliott - Oxford University Press |url=https://global.oup.com/ukhe/product/biochemistry-and-molecular-biology-9780198768111 |access-date=2024-01-04 |website=global.oup.com |language=en}}</ref> , and is the basis of [[Enzyme|enzymology]]).

==BetaSalt bondingbridge==

where ''d'' = electric dipole moment, <math>\varepsilon_0</math> = permitivitypermittivity of free space, <math>\varepsilon_r</math> = dielectric constant of surrounding material, ''T'' = temperature, <math>k_\text{B}</math> = Boltzmann constant, and ''r'' = distance between molecules.

This comparison is approximate. The actual relative strengths will vary depending on the molecules involved. For instance, the presence of water creates competing interactions that greatly weaken the strength of both ionic and hydrogen bonds.<ref>{{Cite book | vauthors last1= Alberts B|first1=Bruce |display-authors=etal |url=https://www.worldcat.org/oclc/887605755 |title=Molecular biology of the cell |date=2015 |isbn=978-0-8153-4432-2 |edition=6th |publisher=[[Garland Science]] - [[Taylor & Francis]] |location=New York, NY |oclc=887605755 }}</ref> We may consider that for static systems, [[Ionic bonding]] and [[covalent bond]]ing will always be stronger than intermolecular forces in any given substance. But it is not so for big moving systems like [[enzyme]] molecules interacting with [[Substrate (chemistry)|substrate]] molecules.<ref>{{cite journal | vauthors = Savir Y, Tlusty T | title = Conformational proofreading: the impact of conformational changes on the specificity of molecular recognition | journal = PLOS ONE | volume = 2 | issue = 5 | pages = e468 | date = May 2007 | pmid = 17520027 | pmc = 1868595 | doi = 10.1371/journal.pone.0000468 | bibcode = 2007PLoSO...2..468S | doi-access = free }}</ref> Here the numerous intramolecular (most often - [[hydrogen bond]]s) bonds form an active intermediate state where the intermolecular bonds cause some of the [[covalent bond]] to be broken, while the others are formed, in this way proccedingproceeding the thousands of [[Enzyme catalysis|enzymatic reactions]], so important for [[Organism|living organisms]].

Intermolecular forces are repulsive at short distances and attractive at long distances (see the [[Lennard-Jones potential]])<ref>{{Cite journal |last1=Fischer |first1=Johann |last2=Wendland |first2=Martin |date=October 2023 |title=On the history of key empirical intermolecular potentials |url=https://linkinghub.elsevier.com/retrieve/pii/S0378381223001565 |journal=Fluid Phase Equilibria |language=en |volume=573 |pages=113876 |doi=10.1016/j.fluid.2023.113876|bibcode=2023FlPEq.57313876F |doi-access=free }}</ref><ref>{{Cite journal |last1=Lenhard |first1=Johannes |last2=Stephan |first2=Simon |last3=Hasse |first3=Hans |date=June 2024 |title=On the History of the Lennard-Jones Potential |url=https://onlinelibrary.wiley.com/doi/10.1002/andp.202400115 |journal=Annalen der Physik |language=en |volume=536 |issue=6 |doi=10.1002/andp.202400115 |issn=0003-3804}}</ref>. In a gas, the repulsive force chiefly has the effect of keeping two molecules from occupying the same volume. This gives a [[real gas]] a tendency to occupy a larger volume than an [[ideal gas]] at the same temperature and pressure. The attractive force draws molecules closer together and gives a real gas a tendency to occupy a smaller volume than an ideal gas. Which interaction is more important depends on temperature and pressure (see [[compressibility factor]]).