Chapter 23, Problem 1ASA

Assign this HSQC Spectrum ( please editing clearly on the image)

(a 4 shows scanning electron microscope (SEM) images of extruded actions of packing bed for two capillary columns of different diameters, al 750 (bottom image) and b) 30-μm-i.d. Both columns are packed with the same stationary phase, spherical particles with 1-um diameter. A) When the columns were prepared, the figure shows that the column with the larger diameter has more packing irregularities. Explain this observation. B) Predict what affect this should have on band broadening and discuss your prediction using the van Deemter terms. C) Does this figure support your explanations in application question 33? Explain why or why not and make any changes in your answers in light of this figure. Figure 4 SEM images of sections of packed columns for a) 750 and b) 30-um-i.d. capillary columns.³

fcrip = ↓ bandwidth Il temp 32. What impact (increase, decrease, or no change) does each of the following conditions have on the individual components of the van Deemter equation and consequently, band broadening? Increase temperature Longer column Using a gas mobile phase instead of liquid Smaller particle stationary phase Multiple Paths Diffusion Mass Transfer

34. Figure 3 shows Van Deemter plots for a solute molecule using different column inner diameters (i.d.). A) Predict whether decreasing the column inner diameters increase or decrease bandwidth. B) Predict which van Deemter equation coefficient (A, B, or C) has the greatest effect on increasing or decreasing bandwidth as a function of i.d. and justify your answer. Figure 3 Van Deemter plots for hydroquinone using different column inner diameters (i.d. in μm). The data was obtained from liquid chromatography experiments using fused-silica capillary columns packed with 1.0-μm particles. 35 20 H(um) 큰 20 15 90 0+ 1500 100 75 550 01 02 594 05 μ(cm/sec) 30 15 10

elow are experimentally determined van Deemter plots of column efficiency, H, vs. flow rate. H is a quantitative measurement of band broadening. The left plot is for a liquid chromatography application and the night is for gas chromatography. Compare and contrast these two plots in terms of the three band broadening mechanisms presented in this activity. How are they similar? How do they differ? Justify your answers.? 0.4 H (mm) 0.2 0.1- 0.3- 0 0.5 H (mm) 8.0 7.0 6.0 5.0 4.0- 3.0 T +++ 1.0 1.5 0 2.0 4.0 Flow Rate, u (cm/s) 6.0 8.0 Flow Rate, u (cm/s)

Predict the products of this organic reaction: + H ZH NaBH3CN H+ n. ? Click and drag to start drawing a structure. X

What is the missing reactant R in this organic reaction? + R H3O+ + • Draw the structure of R in the drawing area below. • Be sure to use wedge and dash bonds if it's necessary to draw one particular enantiomer. Click and drag to start drawing a structure.

What would be the best choices for the missing reagents 1 and 3 in this synthesis? 1 1. PPh3 2. n-BuLi 2 • Draw the missing reagents in the drawing area below. You can draw them in any arrangement you like. • Do not draw the missing reagent 2. If you draw 1 correctly, we'll know what it is. • Note: if one of your reagents needs to contain a halogen, use bromine. Click and drag to start drawing a structure.

The product on the right-hand side of this reaction can be prepared from two organic reactants, under the conditions shown above and below the arrow. Draw 1 and 2 below, in any arrangement you like. 1+2 NaBH₂CN H+ N Click and drag to start drawing a structure. X $