Synthesis and Antimicrobial Activity of N-(6-Carboxyl Cyclohex-3-ene Carbonyl) Chitosan with Different Degrees of Substitution

Table 1

Chemical structure and properties of chitosan and its derivatives with tetrahydrophthalic anhydride [N-(6-carboxyl cyclohex-3-ene carbonyl) chitosan] at different mol ratios (see Scheme 1).

Compound	THPA/mol; GlcN	DA	DDA	DS	FW	Yield; (%)	Intrinsic viscosity (η)	Average MW (Da); ×10^5
Chitosan	—	0.09	0.91	—	164.78	—	4.77	2.76
1	0.1	0.07	0.84	0.09	177.27	84.79	5.09	3.01
2	0.3	0.08	0.74	0.18	191.58	86.01	5.59	3.39
3	0.5	0.06	0.68	0.26	203.63	94.86	6.18	3.87
4	0.8	0.07	0.62	0.30	210.14	96.43	6.47	4.11
5	1.0	0.06	0.54	0.40	224.70	97.11	7.20	4.74

THPA = tetrahydrophthalic anhydride. GlcN = glucosamine. DA is a degree of acetylation (calculated as 1 − DDA). DDA is a degree of deacetylation. DS is a degree of substitution. FW is a formula weight. MW is the molecular weight in g/mol and it was determined for chitosan by measuring its intrinsic viscosity according to the Mark-Houwink-Sakurada equation and it was calculated for compounds 1–5 as follows: yield was determined by weight recovery in accordance with the change in FW.