**Mirosław Jabło ´nski †**

*Review*

Faculty of Chemistry, Nicolaus Copernicus University in Toru ´n, 87-100 Toru ´n, Poland; teojab@chem.umk.pl; Tel.: +48-056-611-4695

† Current address: 7-Gagarina St., 87-100 Toru ´n, Poland.

Academic Editor: Maxim L. Kuznetsov Received: 4 November 2020; Accepted: 23 November 2020; Published: 25 November 2020

**Abstract:** This article is probably the first such comprehensive review of theoretical methods for estimating the energy of intramolecular hydrogen bonds or other interactions that are frequently the subject of scientific research. Rather than on a plethora of numerical data, the main focus is on discussing the theoretical rationale of each method. Additionally, attention is paid to the fact that it is very often possible to use several variants of a particular method. Both of the methods themselves and their variants often give wide ranges of the obtained estimates. Attention is drawn to the fact that the applicability of a particular method may be significantly limited by various factors that disturb the reliability of the estimation, such as considerable structural changes or new important interactions in the reference system.

**Keywords:** intramolecular interaction; interaction energy; hydrogen bond
