Mauro Mocerino

The development of a two-tier multiple-choice diagnostic instrument for evaluating secondary school students’ ability to describe and explain chemical reactions using multiple levels of representation

A 15-item two-tier multiple-choice diagnostic instrument was developed to evaluate secondary students’ ability to describe and explain seven types of chemical reactions using macroscopic, submicroscopic and symbolic representations. A mixed qualitative and quantitative case study was conducted over four years involving 787 Years 9 and 10 students (15 to 16 years old). The instrument was administered to sixty-five Year 9 students after nine months of instruction to evaluate their use of multiple levels of representation. Analysis of the students’ responses demonstrated acceptable reliability of the instrument, a wide range of difficulty indices and acceptable discrimination indices for 12 of the items. The teaching program proved to be successful in that in most instances students were able to describe and explain the observed changes in terms of the atoms, molecules and ions that were involved in the chemical reactions using appropriate symbols, formulas, and chemical and ionic equations. Nevertheless, despite the emphasis on multiple levels of representation during instruction, 14 conceptions were identified that indicated confusion between macroscopic and submicroscopic representations, a tendency to extrapolate bulk macroscopic properties of substances to the submicroscopic level, and limited understanding of the symbolic representational system. [Chem. Educ. Res. Pract., 2007, 8 (3), 293-307.]

Proline-functionalised calix[4]arene: an anion-triggered hydrogelator

A water-soluble, chiral calix[4]arene has been found to form hydrogels when triggered by the presence of specific anions, with efficacy linked to the Hofmeister series; the gel properties are modified by the associated cations, and gelation can be reversibly switched off by increasing pH.

A brief review of Cn-symmetric calixarenes and resorcinarenes

Calixarene and resorcinarene macrocycles are renowned for their ability to form inclusion complexes or act as molecular scaffolds. The addition of chirality to these non-planar molecules is an exciting enhancement of their already robust potential, offering much promise as ligands for chiral catalysis and enantioselective separations. Chiral calixarenes can be produced by the attachment of a chiral moiety or by the placement of an achiral functionality on the macrocyclic structure so as to render it asymmetric. The latter method is particularly intriguing, often resulting in molecules which have C n dissymmetry. This review describes examples of the C n -dissymmetric calixarenes and resorcinarenes prepared to date and discusses aspects of their chirality, including their pictorial and written descriptors.

Students’ perceptions of the role of models in the process of science and in the process of learning

The purpose of this paper was to investigate students’ views on models and modelling in science as well as the role that models play in learning, using a theoretical framework of models in learning. Students’ views on models in science were investigated using a pencil‐and‐paper questionnaire given to 275 students from Grade 8 (13 years old) to first‐year university students, which enabled both forced choice and an open response. The results provided evidence, improving with increased years of schooling, that many students have a good understanding of the role of models in the process of science, appreciating the representational nature of models, the multiplicity of models and the changing nature of models. However, in contrast to previous studies, many students were also aware of the role of models in their learning of science. While some students had a fascination for true facts and single and correct models, others exhibited more sophisticated epistemologies of science. Mostly students’ comments revealed developing understandings of the process of science. Scientific models were associated with students’ understanding of the role of scientific models in the process of science and teaching models were more commonly associated with students’ understanding of the role of models in the process of learning.

Learning at the Sub-micro Level: Structural Representations

This chapter examines the importance of visualisation and language, both verbal and pictorial, on the understanding of the sub-microscopic level of chemistry. We begin by examining what is meant by the term ‘sub-microscopic level’ and how it is different from the macroscopic level. Here we stress the need for the careful use of language to distinguish the two levels and we provide some examples of how the imprecise use of language can blur this distinction. The challenges associated with the description and depictions of the arrangement of electrons in atoms, ions and molecules are then addressed. For a good understanding of chemistry it is critical that students visualise chemical reactions as multiple particle processes and examples are provided where misconceptions arise from a single particle perspective. The need for students to learn, and instructors/textbooks to explain, the conventions and styles of molecular representations is then highlighted. Without a good understanding of the meaning of these forms of molecular representations, students cannot visualise spatial/structural features of a molecule or consider implications of these features on reactivity. Finally we return to the need for a clear distinction between the sub-microscopic ‘reality’ and their representations.

Remarkable thallium(I) selectivity for ion sensors based on π-coordination of calix[4]arene neutral carriers

Calix[4]arene derivatives have been applied as neutral carriers for thallium(I)-selective electrodes, taking advantage of their π-coordination. Calix[4]arene derivatives without any t-butyl group at the upper rim, such as calix[4]arene tetra(propyl ether) and tetra(allyl ether), provided the thallium(I)-selective electrodes with high sensitivity and ion selectivity. t-Butylcalix[4]arene derivatives employed here did not afford very good results as for the thallium(I) neutral carrier. 1H-NMR spectroscopy indicated that thallium(I) complexation by the calixarene neutral carriers is made primarily by π-coordination of their skeletal aromatic rings. The ion-selective electrode based on calix[4]arene tetra(propyl ether) was successfully applied to thallium(I) assays in human urine.

Variations on a Cage Theme: Some Complexes of Bicyclic Polyamines as Supramolecular Synthons

Dedication: One of Alan Sargeson’s great abilities was to seek out knowledge on topics of which he was not the master from those people with the expertise. This led occasionally to publications with a ‘cricket team’ of authors but with a rich brew of information, often international. Alan also insisted that all authors were equal since, without any one, the paper would not be what it was. Hence, he endeavoured to pursue the policy, difficult to maintain over a period where an obsession with absurdities such as the order of authors and point-scoring based on meaningless publication indices became so important in the maintenance of research, of listing authors simply in alphabetical order. In describing work begun while he was still with us, we have attempted to adhere to his principles. Analysis of a body of crystallographic information concerning metal(ii) and metal(iii) complexes of macrobicyclic hexamine ligands and some of their derivatives provides evidence for the action of a variety of intermolecular forces within the lattices. Hydrogen bonding is universal and its forms depend strongly upon the oxidation state and the particular nature of the metal ion bound to the macrobicycle. The introduction of both aliphatic and aromatic substituents leads to lattices in which these substituents associate, although, in the case of aromatic substituents, this is not necessarily a consequence of ‘π-stacking’, despite the fact that the aromatic ring planes form parallel arrays. At least in the case of CoIII, stable enantiomers of the complexes can be obtained, and in {Δ-(+)589-[Co{(NH3)(CH3)sar}]}2Cl2(C6(CO2)6)·26H2O (sar = 3,6,10,13,16,19-hexa-azabicyclo[6.6.6]icosane), the benzene hexacarboxylate anion adopts a chiral conformation in the presence of the optically active cation.

Functionalization of Cage Amines with Pendant Aromatic and Heteroaromatic Substituents

Structural studies have confirmed that it is possible to exploit the relatively low nucleophilicity of the “external” amino substituents on the CoIII complex of 1,8-diaminosarcophagine (“sarcophagine” = sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) in acylation and alkylation reactions leading to a variety of functionalized cage amine complexes. With the appropriate choice of solvent, all these reactions can be conducted with high efficiency, and the new complexes display properties foreshadowing the application of cage systems in, for example, electroactive polymers.

Students’ attitudes, self-efficacy and experiences in a modified process-oriented guided inquiry learning undergraduate chemistry classroom

This one-semester, mixed methods study underpinning social cognition and theory of planned behaviour investigated the attitudes, self-efficacy, and experiences of 559 first year undergraduate chemistry students from two cohorts in modified process-oriented guided inquiry learning (POGIL) classes. Versions of attitude toward the study of chemistry (ASCI v2), and chemistry attitudes and experiences questionnaire (CAEQ) were adopted, modified, and administered to understand and gauge students’ affective outcomes before (pre) and after (post) POGIL intervention. Students’ post-POGIL perceptions of their attitudes, self-efficacy and experiences were statistically significantly higher. In addition to confirmatory testing of reliability of data obtained from ASCI v2 and CAEQ in an Australian POGIL context, the findings suggest that POGIL intervention provides positive affective experiences to students who are new to chemistry or have limited prior chemistry knowledge.

Rare-earth-metal solvent extraction with calixarene phosphates

Several phosphate esters in which calixarenes act as either uni- or bi-dentate ligands towards PV have been investigated as solvent-extraction agents for the rare-earth metals (La to Lu, excluding Pm, plus Y). Extraction of picrate salts into dichloromethane, ethyl acetate and tributyl phosphate–hexane (1 : 1) is considerably enhanced by some of these esters but in no case is any marked selectivity exhibited, although some features of the observed extraction patterns suggest ways in which the molecular design of such extractants may be improved. Crystal structure determinations on two phosphate esters in which the calixarene unit is bidentate indicate that the relatively poor metal-ion binding abilities of these ligands may be a consequence of a preferred orientation of the phosphoryl donor groups in which they diverge from the macrocyclic ring. A crystal structure determination on the 2 : 1 complex of tetrakis-O-(diethoxyphosphoryl)-p-tert-butylcalix[4]arene and lanthanum picrate (2,4,6-trinitrophenolate) shows that a convergent array of phosphoryl donor groups can form in such cases where the functional groups are flexible. This does not, however, appear to lead to a particular enhancement of stability, as the complex readily dissociates into a 1 : 1 species in solution.