Download CH450 Class Assignment 5 Materials and Methods

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CH450 Class Assignment 5 – Materials and Methods
Correct or rewrite the following excerpts from the Materials and Methods (Experimental)
sections of published papers, according to the guidelines discussed in class. There
should already be no spelling or other errors and the organization and style is correct for
the particular journal. Include in your answer notes on any omissions, and correct any
inconsistencies of style.
1. (A synthesis subsection from the Experimental section of a synthetic organic
chemistry paper)
3-Hydroxymethyl-2-tert-butyldiphenylsilyloxymethyloxirane 14
A solution of alkene 13 (35 g, 0.11 mol) in CH2Cl2 (100 ml) was added to a stirred solution of
m-chloroperbenzoic acid (52.5 g, 0,15 mol) in CH2Cl2 (250 ml) over 0.5 h. After 36 h, the solution
was cooled to 0 oC to precipitate m-chlorobenzoic acid, which was removed by filtration. Water
was added and the separated organic layer was washed with aqueous Na2SO3 (2 x 350 ml),
aqueous NaHCO3 (3 x 350 ml) and brine (300 ml). It was dried over Na2SO4 and the solvent
was evaporated. Purification by flash chromatography (conditions should be included, e.g.
silica gel, ethyl acetate) provided epoxide 14 (36.72 g, 100%) as a colourless oil;
max(CHCl3)/nm 214, 226, 266; max (conditions (liquid film, solution, etc)/units (cm -1) needed)
3426, 3070, 3048, 3012, 2996, 2954, 2933, 2892, 2859, 1589, 1471, 1428, 1391, 1361, 1260,
1188, 1109, 1091, 1046, 975, 937; 1H NMR (300 MHz, CDCl3) /ppm 7.72 (4H, m, ArH), 7.45
(6H, m, ArH), 4.0-3.75 (4H, m, H-2,3 and CH2OH), 3.28 (2H, m, CH2OSi), 1.92 (1H, br s, OH), 1.1
(9H, s, t-Bu); 13C NMR (75 MHz, CDCl3) /ppm 135.5, 135.4, 132.9, 132.7, 130.0, 127.8, 62.1,
60.7, 56.3, 56.1, 26.7, 19.1; m/z 360 (MNH4+, 100%), 343 MH+, 50%); found MNH4+ 360.1991.
C20H26O3Si + NH4+ requires 360.1995. The spectroscopic data were exactly comparable with
those reported previously29 for this compound prepared in homochiral form using Sharpless’
method.
2. (Two subsections from the Experimental section of an analytical chemistry
paper)
2.1. Reagents and standards
Acetonitrile, methanol and water, of HPLC grade, and acetic acid (maybe grade) were supplied
by VWR International (location needed). Trans-resveratrol (grade) was acquired from Sigma
(location).
2.3. HPLC Analysis
The analyses were performed using a Waters liquid chromatograph (location, model needed)
equipped with a pump and a gradient controller (models needed), to which were connected an
autosampler and a photodiode-array detector (models needed). The columns were a series of
two Chromolith Performance RP-18e from VWR International (column dimensions needed).
The work was done by means of coupled columns, which feature a theoretical plate number
sufficient to separate the four forms of resveratrol. All runs were acquired and processed using
Millenium32 software. (company name and version needed) Details of injection volume
needed somewhere.
The solvent system used was a gradient of (A) water-acetic acid (94:6) (v/v) and (B) wateracetonitrile-acetic acid (65:30:5). The elution gradient is shown in Table 1. Use of monolithic
columns permitted mobile phase flow-rate of up to 7 ml/min to be employed in assays. Increasing
the flow rate to 7 ml/min significantly increased the speed of the assay and consequently reduced
run time. (This sentence can be omitted and transferred to early Discussion section)
Spectroscopic detection, covering the UV-vis range of 200-310 nm was performed with a
resolution of 1.2 nm, and the quantitation was carried out at 285 and 306 nm (where cis- and
trans- isomers have absorbance maximum, respectively).