Table 11: Descriptions of substructure and which properties their existence would affect. Molecules containing X substructure are usually named as "X-Compounds", "X derivatives" and "X moieties".
Substructure	Description & Affected molecular properties
allylic	Allylic oxidations have featured in hundreds of chemical syntheses, due to their particular electrochemical properties [100–102].
amide	An amidine is a compound with the general formula RC(=O)NR’R”, where R, R’, and R” represent organic groups or hydrogen atoms. It has significant impacts on the mechanical, acid-base, and solubility properties of molecules [wikipage].
amidine	Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). Amidines are much more basic than amides and are among the strongest uncharged/unionized bases. Several drug or drug candidates feature amidine substituents. Examples include the antiprotozoal Imidocarb, the insecticide ameritz, the anthelmintic tribendimi-dine, and xylamidine, an antagonist at the 5HT2A receptor [wikipedia].
Azo	Azo compounds are compounds bearing the functional group diazenyl R-N=N-R', in which R and R' can be either aryl or alkyl. Certain azo compounds are known to have antibiotic, antiviral, antifungal, antineoplastic, and cytotoxic prop-erties [103].
benzene	Benzene (aromatic rings) is an organic chemical compound with the molecular formula C6H6. Aromatic rings are important residues for biological interactions and appear to a large extent as part of protein-drug and protein-protein interactions. They are relevant for both protein stability and molecular recognition processes due to their natural occurrence in aromatic aminoacids (Trp, Phe, Tyr and His) as well as in designed drugs since they are believed to contribute to optimising both affinity and specificity of drug-like molecules [104].
epoxide	An epoxide is a cyclic ether with a three-atom ring. Epoxide-containing molecules have therapeutic value. The main therapeutic interest is as anticancer agents. The main mechanisms are enzyme inhibition, induction of cell cycle arrest, apoptosis. Other therapeutic interests are for heart failure, infections, gastro-intestinal diseases [105].
ether	Ethers are a class of organic compounds that contain an ether group-an oxygen atom connected to two alkyl or aryl groups. They have the general formula R-O-R', where R and R' represent the alkyl or aryl groups. The C-O bonds that comprise simple ethers are strong. They are unreactive toward all but the strongest bases. Although generally of low chemical reactivity, they are more reactive than alkanes. Some important reactions include cleavage, peroxide formation, lewis bases, and alpha-halogenation[wikipedia].
furan	Furan is a heterocyclic organic compound, consisting of a five-membered aro-matic ring with four carbon atoms and one oxygen atom. The furan ring present in the chemical structures may be one of the domineering factors to bring about the toxic response resulting from the generation of reactive epoxide or cis-enedial intermediates which are of the potential to react with biomacro-molecules [106, 107].
guanido	Guanidine is the compound with the formula HNC(NH2)2. It is a colourless solid that dissolves in polar solvents. It is a strong base that is used in the production of plastics and explosives. Most guanidine derivatives are in fact salts containing the conjugate acid[wikipedia]. Guanidine-containing derivatives constitute a very important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases [108].
halogen	The halogens are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Halogens are highly reactive, and as such can be harmful or lethal to biological organisms in sufficient quantities. This high reactivity is due to the high electronegativity of the atoms due to their high effective nuclear charge[wikipedia]. A significant number of drugs and drug candidates in clinical development are halogenated structures. For a long time, insertion of halogen atoms on hit or lead compounds was predominantly performed to exploit their steric effects, through the ability of these bulk atoms to occupy the binding site of molecular targets [109].
imidazole	Imidazole is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. This ring system is present in important biological building blocks, such as histidine and the related hormone histamine. Many drugs contain an imidazole ring, such as certain antifungal drugs, the nitroimidazole series of antibiotics, and the sedative midazolam[wikipedia].
imide	In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. Being highly polar, imides exhibit good solubility in polar media. The N-H center for imides derived from ammonia is acidic and can participate in hydrogen bonding. Unlike the structurally related acid an-hydrides, they resist hydrolysis and some can even be recrystallized from boiling water[wikipedia]. Immunomodulatory imide drugs (IMiDs) are a class of immunomodulatory drugs (drugs that adjust immune responses) containing an imide group.
lactam	A beta-lactam (β-lactam) ring is a four-membered lactam. The β-lactam ring is part of the core structure of several antibiotic families, the principal ones being the penicillins, cephalosporins, carbapenems, and monobactams, which are, therefore, also called β-lactam antibiotics [wikipedia].
morpholine	Morpholine is an organic chemical compound having the chemical formula O(CH2CH2)2NH. Morpholine is a heterocycle featured in numerous approved and experimental drugs as well as bioactive molecules. It is often employed in the field of medicinal chemistry for its advantageous physicochemical, biologi-cal, and metabolic properties, as well as its facile synthetic routes [110].
NO (hydrox-ylamine)	Hydroxylamine is an organic compound with the formula NH 2OH. The material is a white crystalline, hygroscopic compound. Hydroxylamines and their deriva-tives are powerful aminating reagents, which are often used for arene C-H and X-H aminations (X=O, N, S, P) as well as Schmidt-type reaction46, serving as alternative ways to introduce amino groups on various chemical skeletons [111].
oxazole	Oxazoles is a doubly unsaturated 5-membered ring having one oxygen atom at position 1 and a nitrogen at position 3 separated by a carbon in-between. Sub-stitution pattern in oxazole derivatives play a pivotal role in delineating the biological activities like antimicrobial, anticancer, antitubercular anti-inflammatory, antidiabetic, antiobesity and antioxidant etc [112].
piperidine	Piperidine is an organic compound with the molecular formula (CH2)5NH. This heterocyclic amine consists of a six-membered ring containing five methylene bridges (−CH2−) and one amine bridge (−NH−). Piperidine and its derivatives are ubiquitous building blocks in pharmaceuticals[26] and fine chemicals. The piperidine structure is found in, for example: Icaridin, SSRIs, stimulants and nootropics, SERM etc. Piperidine is also commonly used in chemical degradatio-nion reactions, such as the sequencing of DNA in the cleavage of particular modi-fied nucleotides. Piperidine is also commonly used as a base for the deprotection of Fmoc-amino acids used in solid-phase peptide synthesis [wikipedia].
piperazine	Piperazine is an organic compound that consists of a six-membered ring contain-ing two nitrogen atoms at opposite positions in the ring. Many currently notable drugs contain a piperazine ring as part of their molecular structure (“Substituted piperazine”). Examples include: Antianginals, Antidepressants, Antihistamines etc [wikipedia].
pyridine	Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. Pyridine moieties are often used in drugs because of their characteristics such as basicity, water solubility, stability, and hydrogen bond-forming ability, and their small molecular size [113]. Pyridine-based ring systems are one of the most extensively used heterocycles in the field of drug design, primarily due to their profound effect on pharmacological activity, which has led to the discovery of numerous broad-spectrum therapeutic agents [114].
tetrazole	Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. Tetrazole derivatives are a prime class of heterocycles, very important to medicinal chemistry and drug design due to not only their bioisosterism to carboxylic acid and amide moieties but also to their metabolic stability and other beneficial physicochemical properties [115].
thiazole	Thiazole, or 1,3-thiazole, is a heterocyclic compound that contains both sulfur and nitrogen. The versatility of thiazole nucleus demonstrated by the fact that it is an essential part of penicillin nucleus and some of its derivatives which have shown antimicrobial (sulfazole), antiretroviral (ritonavir), antifungal (abafungin), antihistaminic and antithyroid activities [116].
thiophene	Thiophene is a heterocyclic compound with the formula C4H4S. In medicine, thiophene derivatives shows antimicrobial, analgesic and anti-inflammatory, antihypertensive, and antitumor activity while they are also used as inhibitors of corrosion of metals or in the fabrication of light-emitting diodes in material science [117].
urea	Urea, also known as carbamide, is an organic compound with chemical formula CO(NH2)2. This amide has two -NH2 groups joined by a carbonyl (C=O) functional group. It has similar effects as amide groups.