Relative retention

Retention times for several organic compounds separated on a gas chromographic column are given below: Compound tR(seconds) Air 75 Pentane 190 Heptane 350 2-Pentene 275 a. Calculate the relative retention of 2-Pentene with respect to pentane. b. Calculate the relative retention of heptane with respect to pentane.

Refractive Index

How does the refractive index of a liquid vary with temperature?? What corrective factor is often used to determine the value at a specific temperature, for example, 20 degrees Celsius, if the measurement were made at 25 degrees Celsius?

Partition Coefficient

A 36-mg sample of an organic compound (MW = 84) is dissolved in 10mL of water. This aqueous solution is extracted with 5.0 mL of hexane. Separation and analysis of the aqueous phase shows that it now contains 12 mg of the organic compound. Calculate the partition coefficient for the compound.

stereochemistry of bromine addition to trans-cinnamic acid; syn or anti addition?

This problem is from Modern Projects and Experiments in Organic Chemistry by Mohrig, Hammond, Schatz, and Morrill. (1) Showing a lot of detail, please draw out the mechanism of the reaction step-by-step for me. (2) Is it syn or anti addition or both? (3) Isn't the erythro diastereomer a meso compound? (4) If my melting points came out about 5 degrees Celsius under the mp of 202-204 recorded below, is it because there was some threo diastereomer in my product?

Percent composition

Gas chromatographic analysis of a mixture of organic compounds gave the following peak areas (sq cm): hexane = 2.7, heptane 1.6, hexanol = 1.8, toluene = 0.5 a. Calculate the mole percent composition of the mixture. Assume that the response of the detector (area per mole) is the same for each component. b. Calculate the weight percent composition of the mixture using the same assumptions as in part a.