â€œMolecularâ€ Molecular Sieves: Lid-Free Decamethylcucurbit[5]uril Absorbs and Desorbs Gases Selectively This work was supported in part by a Grant-in-Aid for COE Research â€œDesign and Control of Advanced Molecular Assembly Systemsâ€ from the Ministry of Education, Science, Sports, and Culture, Japan (#08CE2005). The authors also thank Prof. T. Shinmyozu of the Institute for Fundamental Organic Chemistry in Kyushu University for use of a Rigaku RAPID X-ray instrument.

Scanning electron beam lithography has been used for a number of years to write submicrometer linewidth patterns in radiation sensitive films (resist films) on substrates. On semi-infinite substrates, electron backscattering severely limits the exposure latitude and control of cross-sectional profile for patterns having fundamental spatial frequencies below about 4000 Å(l),Recently, STEM'S have been used to write patterns with linewidths below 100 Å. To avoid the detrimental effects of electron backscattering however, the substrates had to be carbon foils about 100 Å thick (2,3). X-ray lithography using the very soft radiation in the range 10 - 50 Å avoids the problem of backscattering and thus permits one to replicate on semi-infinite substrates patterns with linewidths of the order of 1000 Å and less, and in addition provides means for controlling cross-sectional profiles. X-radiation in the range 4-10 Å on the other hand is appropriate for replicating patterns in the linewidth range above about 3000 Å, and thus is most appropriate for microelectronic applications (4 - 6).

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Organic chemistry lecture course and exercises based on true scale models

Chemistry Teacher International ◽

10.1515/cti-2019-0006 ◽

2020 ◽

Vol 0 (0) ◽

Author(s):

Felix Lederle ◽

Eike G. Hübner

Keyword(s):

Organic Chemistry ◽

Bond Length ◽

3D Models ◽

Poly Lactic Acid ◽

X Ray ◽

Bond Angles ◽

Chemical Structures ◽

Scale Models ◽

Hands On ◽

Scaled Models

Abstract3D models of chemical structures are an important tool for chemistry lectures and exercises. Usually, simplified models based on standard bond length and angles are used. These models allow for a visualized discussion of (stereo)chemical aspects, but they do not represent the true spatial conditions. 3D-printing technologies facilitate the production of scale models. Several protocols describe the process from X-ray structures, calculated geometries or virtual molecules to printable files. In contrast, only a few examples describe the integration of scaled models in lecture courses. True bond angles and scaled bond lengths allow for a detailed discussion of the geometry and parameters derived therefrom, for example double bond character, aromaticity and many more. Here, we report a complete organic chemistry/stereochemistry lecture course and exercise based on a set of 37 scale models made from poly(lactic acid) as sustainable material. All models have been derived from X-ray structures and quantum chemical calculations. Consequently, the models reflect the true structure as close as possible. A fixed scaling factor of 1 : 1.8·108 has been applied to all models. Hands-on measuring of bond angles and bond length leads to an interactive course. The course has been evaluated with a very positive feedback.

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