Bis(4,6-diaminopyrimidin-2-yl) disulfide dimethyl sufoxide disolvate

The title compound, C8H10N8S2·2C2H6SO, was obtained unintentionally during an attempt to prepare a thiol-ate derivative of trimethyl-tin. The complete disulfide mol-ecule is generated by twofold rotation symmetry and the C - S - S - C torsion angle around the S - S bond is -85.70 (10)°. The mol-ecules are connected via N - H⋯N hydrogen bonds into strongly corrugated layers parallel to (001), generating an R 2 2(8) motif. The solvent mol-ecule, which exhibits minor disorder of its S atom [site occupancies = 0.9591 (18) and 0.0409 (18)], is linked to this layer via a pair of N - H⋯O inter-actions

PROMETHEAN RESPONSE OF GREEK HIGH-SCHOOL STUDENTS TO THE PROTEAN CHANGES OF THE CHEMISTRY CURRICULUM

Abstract The response of the Greek high-school students to the ever-changing educational program and especially their chemistry curriculum involves the adoption of the "memorize or reject" attitude rather than the assimilation of facts and laws into their scientific background. Two recent studies carried out during school years 2010-11 and 2013-1

LIVING WITH PRECONCEPTIONS. DOES MORE TEACHING AND LAB EXPERIMENTING HELP TO IMPROVE CHEMICAL PRINCIPLES ASSIMILATION?

A survey is carried out on first year students of Science Departments at a Greek university, in relation to knowledge of basic chemical principles, following a semester of lectures and tutorials within the General Chemistry class. The findings attempt to correlate the assimilation of information with the curriculum adopted by the school of study and the intensity of teaching both in lecture hours and in laboratory experiments carried out

UTILIZATION OF THE EXPERIMENT WITHIN THE CLASSROOM. SEEKING TO DEVELOP UNDERSTANDING OVER LOVE TOWARDS CHEMISTRY

A series of simple experiments is described, for presentation in the secondary school classroom aiming at the development of understanding Chemistry by the students rather than provoking “love” for the topic. The experiments present modifications of known procedures adaptable to practically any point of secondary education and to any level of sophistication provided by the school facilities. The simplicity, clarity of the procedures and security of the students are the factors considered as central relative to thrilling which has been a distractor in many related projects. Emphasis is placed on solutions, and especially the description of their concentration and the understanding of the meaning of the various forms this description may possess. The experiments are also related to discussions and queries which are designed to promote active thinking and develop both practical and mental skills among the students

LIVING WITH PRECONCEPTIONS. RESPONSE TO PH AND RELATED ASPECTS OF FIRST YEAR UNIVERSITY STUDENTS THROUGH THE POINT OF VIEW OF THEIR HIGH SCHOOL CURRICULUM

A survey is contacted on a limited number of first year students at a Greek university (n=54) in relation to their notions about pH and related aspects, following a semester of lectures and tutorials, both of which include teaching and experimenting upon pH. The findings attempt to correlate the assimilation of information with the school of study and with the kind of underlying background of the students since they could, in principle, have followed different high school currliculae towards entering the university courses. Namely, students who followed a curriculum termed “technological direction” in high school could follow studies at the Geology department where limited knowledge and use of pH is required at the undergraduate level, while the high school direction does not involve any Chemistry classes at all in the final year. On the other hand, Pharmacy students are overloaded with chemical information and can enter the department course only through a high school direction termed “positive”, which involves a lot of lessons on equilibrium and pH

STOICHEIOMETRY WITHIN THE FRAMEWORK OF GREEK SECONDARY EDUCATION CHEMISTRY CURRICULUM

A study is carried out by means of distributing a duo of questionnaires to secondary education students in a variety of schools in Northern Greece. The first of these questionnaires is aiming at the identification of the initial degree of general chemical concepts and ideas assimilation by the students and is distributed by their teachers during an early teaching hour in the senior high-school grade B class. The second questionnaire is distributed during the final weeks of the school year and aims at the mapping of integration of concepts related to stoicheiometry to students’ chemical background, since grade B of senior high-school is loaded with introductory organic chemistry and the corresponding wide variety of reactions on which a vast amount of problems to be solved is based. The validity of the questionnaires and their efficiency in fulfilling the scope of the current research is carried out by means of the application of certain post-statistical indices with the final goal being their utilization as a diagnostic tool for probing student understanding of chemical concepts

A PICTURE PROVOKES A THOUSAND THOUGHTS. ARE THEY ALL RIGHT?

Cave illustrations from the prehistoric period used to tell stories of hunting and of rituals and even today provide us with a satisfactory view of how our ancestors lived many centuries ago. In this sense, illustrations in books help to make the content more easily understood whether the content is a fiction story or a scientific textbook. In scientific textbooks especially, pictorial representations are used widely in order to clarify relationships between measurable quantities and even between observables and more abstract ideas. However, pictures and diagrams are not free from misinterpretations and/or oversimplifications, therefore provoking a series of thoughts which can create or maintain logical deductions not strictly true within the scientific realm studied. It is therefore, not straightforward and always true that a picture has an equivalent of thousand words and may be used accordingly. In Chemistry textbooks we have identified several cases where pictorial representations may give rise to misconceptions which could and should be avoided. In most of the cases discussed there is a way to overcome such effects with low cost and high applicability amendments, a few of which are proposed in the text

CLASSROOM EXPERIMENTS AS SOLUTION FOR UNDERSTANDING SOLUTIONS

Validation is provided to the assumption that Chemistry, being an experimental subject taught to secondary education students, is better understood via the performance of relevant experiments within the classroom. The case of solution Chemistry, especially solubility, description of solutions in terms of their concentration as well as estimation of concentrations following dilution or mixing is studied by means of a questionnaire addressed to first year senior high school students who have been exposed to varying degree of experimentation during their junior high school studies. The questionnaire is tested as of its validity for drawing conclusions and of its potential use as a test for future evaluation of senior high school students referring to their understanding of nomenclature and properties of solutions. A total of 208 students in three different schools in Northern Greece have been subjected to the study

NUMERICAL VALUES OF UNITS AND QUANTITIES IN UNDERSTANDING BASIC CHEMICAL PRINCIPLES

A proposal is made to conduct discussions and carry out simple mathematical tasks in the chemistry laboratory targeting the understanding of the magnitude of various constants and/or quantities which are described and frequently used by first year undergraduate students. Examples are presented about the numeric and/or descriptive procedures utilized to clarify the meaning of expressions and the actual “size” of quantities which are involved in a number of chemical laboratory applications, within the framework of an introductory general chemistry class

PERSONAL FACTORS INFLUENCING THE UNDERSTANDING OF SCIENTIFIC TEXTS

Teaching Science is aided, throughout the educational system, by the study of appropriate textbooks. The content of the textbook used for a specific course plays a considerable role to the degree of the assimilation of the topics addressed by it; however, the actual way it is viewed by the readers/students is also expected to be a major factor. In the current study a double-page spread text is introduced to students of Chemistry. The topic described concisely is related to catalysis and the text is accompanied by a variety of visual aids (graph, algebraic equations, 2D chemical formula, diagram, table). The fifty students participating in the survey are covering the whole range from first-year undergraduates to postgraduates and they are tested for their comprehension of the text provided. The extent of this comprehension is correlated to their logical thinking, field dependence/independence and prior knowledge of the topic as they emerge from assessment of separate preliminary tests they have taken in advance