ПРИЛОЗИ, Одделение за природно-математички и биотехнички науки, МАНУ, том 34, бр. 1–2, стр. 27–32 (2013) CONTRIBUTIONS, Section of Natural, Mathematical and Biotechnical Sciences, MASA, Vol. 34, No. 1–2, pp. 27–32 (2013) Received: July 30, 2013 ISSN 1857-9027 Accepted: September 12, 2013 UDC: 37.016:[547.917:542.943 Educational paper MISCONCEPTIONS IN THE CHEMISTRY TEACHING IN THE REPUBLIC OF MACEDONIA REGARDING THE OXIDATION REACTIONS OF MONOSACCHARIDES Marina Stojanovska 1* , Bojan Šoptrajanov 2 , Vladimir M. Petruševski 1 1 Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University, Skopje, Republic of Macedonia 2 Macedonian Academy of Sciences and Arts, Skopje, Republic of Macedonia *Corresponding author, e-mail: marinam@pmf.ukim.mk The easy oxidation of the substances containing aldehyde groups using a mild oxidizing agents, such as solutions containing copper(II) or silver(I) ions, can provide a mean to detect the presence of carbohydrates known as reducing sugars. However, using such tests, it is not possible to distinguish between aldoses and ketoses because the alkaline conditions in the reaction system lead to tautomerization of the α-hidroxyketone and immediate oxidation of the product so that both glucose and fructose will react with the oxidizing agents (the Tollens’ and Fehling’s reagents). In fact, the reaction of fructose is even faster than that of glucose. A misinterpretation or simple neglect of these experimental facts is present in some textbooks in the Republic of Macedonia and this influences the chemistry teaching by creating misconceptions among students and teachers. Key words: misconceptions; monosaccharides; Tollens’ and Fehling’s reagents; reducing sugars; chemistry teaching INTRODUCTION There are many terms that refer to students’ erroneous notions, although the prevalent one is misconceptions. The term "misconception" could be defined as "an idea which is wrong because it has been based on a failure to understand a situation" [1]. The erroneous notions can be formed previously, outside school (preconcepts) but can also stem from the elements of the teaching process itself (school- made misconceptions) [2]. There are numerous studies of misconceptions in chemistry [2–6 and the references therein]. Deeming that the above topic is interesting, important and more than relevant for the contemporary chemical education research, we devoted some of our studies to chemistry misconceptions [7]. While investigating misconceptions among students we came across one school-made misconception and the present contribution is devoted to it – the oxidation reactions of monosaccharides. Namely, we found that several textbooks used in the Republic of Macedonia include information on glucose and fructose and their characteristic reactions including those with the Tollens’ or Fehling’s reagents. Some authors [8, 9] mention only the reaction of the Tollens’ or Fehling’s reagent with glucose but not that with fructose while others [10] state that the reaction with the Fehling’s reagent is possible only with glucose, but not with fructose, this being, allegedly, a direct evidence that glucose contains aldehyde groups in its molecules and fructose does not. However, if the teacher carries out the corre- sponding reactions in front of his/her students, he/she will be faced with the unexpected result that can be personally very unpleasant: both glucose and fructose will react. Obviously, the statements found in the textbook [10] can lead to development of misconceptions among students and teachers. The reason why fructose indeed reacts with the mentioned reagents is the molecular rearrangement called tautomerization of the α-hydroxyketones under