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Small molecules (up to ca. 1000 atoms) usually form better-ordered crystals than large molecules, and thus it is possible to attain lower R-factors. In the Cambridge Structural Database of small-molecule structures, more than 95% of the 500,000+ crystals have an R-factor lower than 0.15, and 9.5% have an R-factor lower than 0.03.
An R F value will always be in the range 0 to 1; if the substance moves, it can only move in the direction of the solvent flow, and cannot move faster than the solvent. For example, if particular substance in an unknown mixture travels 2.5 cm and the solvent front travels 5.0 cm, the retardation factor would be 0.50.
COOH, R, NH 2 and H (where R is the side-chain) are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO→R→N groups around the carbon atom as center is counter-clockwise, then it is the L form. [14] If the arrangement is clockwise, it is the D form. As usual, if the ...
R and R' represent most organyl substituents. In organic chemistry, ethers are a class of compounds that contain an ether group—a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula R−O−R′, where R and R′ represent
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
Coefficient of relationship (r), in biology; Effective reproduction number (R), the number of cases generated by one case in the current state of a population in epidemiology Basic reproduction number (R 0), the expected number of cases directly generated by one case; Haplogroup R (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup
The term "R-loop" was given to reflect the similarity of these structures to D-loops; the "R" in this case represents the involvement of an RNA moiety. In the laboratory, R-loops can be created by transcription of DNA sequences (for example those that have a high GC content) that favor annealing of the RNA behind the progressing RNA polymerase. [1]
T is the temperature, T TPW = 273.16 K by the definition of the kelvin at that time; A r (Ar) is the relative atomic mass of argon and M u = 10 −3 kg⋅mol −1 as defined at the time. However, following the 2019 revision of the SI , R now has an exact value defined in terms of other exactly defined physical constants.