Projection Halogen

Organic Chemistry HELP PLEASE!?

1. Xomine is a newly discovered halogen from planet X. (The elemental symbol
is X, its name is pronounced “so mean”.) The compound 2-xomobutane can exist
in three low-energy conformations with respect to the C2-C3 bond.
a. Draw Newman projections of the three low-energy rotational isomers.
b. It was found that the rotational isomer in which the C4 methyl group is gauche
to the -X substituent (only) is exactly three times as likely to be found as the
rotational isomer in which the C4 methyl group is gauche to the C1 methyl group
(only). If the value of E (the steric crowding energy) for a gauche methyl-methyl
interaction is +0.90 kcal/mole, calculate the value of E for a gauche methyl-X
interaction.
c. Calculate the percentage of molecules that will be in the conformation where
the C4 methyl group is gauche to both –X and C1, simultaneously.

1a. You need to look up in your textbook how to draw Newman projections. You draw a circle. The “front” will have three bonds going into the center of the circle, pointing in the directions of 12 o’clock, 4:00 and 8:00. I’ll call those positions A, B, and C. The “back” will have three bonds going just to the edge of the circle, pointing to 2:00 6:00 and 10:00. I’ll call those positions D, E, and F. One rotamer has a methyl group at A, xomine at D, methyl at E. Another has methyl group at A, xomine at E, methyl at F. There is a third isomer which has methyl at A, xomine at F, and methyl at D, but this has two gauche interactions and is apparently excluded from consideration in the subsequent calculations. All the other positions are hydrogens. I just realized that if you are looking at the C2-C3 bond, that I put the xomine on C3, but it’s the same compound as if the xomine was on C2.
1b. You need to know the Boltzmann Distribution for this. The equation is N(1)/N(0) = exp(-DE/RT). R = 1.987 cal/K/mol. Thus you are solving for DE (delta E), and that is DE = -RT ln (N(1)/N(0)). But N(1) / N(0) = 1/3, that is the ratio you’re given for the two populations. So DE = 1.984 * 298 ln(1/3) = 650 cal/mol = 0.65 kcal/mol. The isomer with the gauche methyl-X interaction is 0.65 kcal/mol higher, so the gauche interaction must be 1.55 kcal/mol.
1c. Okay now the other isomer comes into play after all. That is where the C1 CH3 is between the C4 CH4 and the C3 xomine. That has both interactions, so the relative energy is 1.55+0.9 = 2.45.
So if the relative number of low energy conformer is 1, then the relative number of next-higher conformations is 0.333. For the last isomer we return to the Boltzmann Distribution, and N(1)/N(0) = exp(-DE/RT) = exp(-1550/1.987*298) = 0.07 or about 7%. Actually if you add 1.00, 0.33, and 0.07 you get 1.4. So the percentages of the three isomers will be 7%, 23%, and 7%.

There was a fair amount of calculating there, and some of that was hard to explain in a text-only format but hopefully that helped.

2. That’s not the bisulfite ion. What you drew will not have a dipole because the resonance structures will direct both negative charges away from each other along an axis that contains the S-S bond.

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Hotel Conference Room Lighting Project

Our client was a large hotel on the East Coast looking to completely replace the existing lighting system in one of their conference rooms. The conference room had recently been renovated creating a clean, open space that could be setup for a variety of functions. With the addition of tables, chairs, benches, or formal dining tables, the conference room could be used for a variety of occasions and special events in addition to seminars and business meetings. The problem was that as soon as renovations were complete, hotel management quickly realized that the conference room had now outgrown the capabilities of its primitive fluorescent lighting system, and that it would require a more advanced source of light in order to attract rentals for all the many events for which it could now be used.

In order to accommodate the complexity of this project, we first asked the hotel to send us a list of the various room orientations that they envisioned. Dinner parties, seminars, group therapy sessions, and business presentation meetings were all included on the very extensive list we received from the client. This indicated to us immediately that we would need to install more than one source of conference room lighting in order to fulfill all of the client’s expectations. We would also need to create multiple switching points to create different layers of light in different portions of the conference room. Mood setting was not the primary goal here, but practical use instead. There were a number of shows coming to town that featured products and activities that tended to attract an older audience. The conference room lighting would need the brightest and most energy efficient lights to host events such as coin shows and other product showcases where detail and high visibility were of the utmost concern. There was also a need for superior color rendering, so another layer of lighting from a halogen source would be necessary to make certain that people could clearly distinguish colors when looking through merchandise.

The conference room also had a small stage where speakers and musical guests periodically performed. The hotel asked us if we could install stage lighting here. Stage lighting equipment is not our normal forte, but we told the hotel we would commit ourselves to developing a solution as part of the overall conference room lighting system.

We simply could not have done this project so effectively without our photometric software. Using IES files on a number of different fixture options, we were able to model dozens of hypothetical lighting scenarios for the conference room’s many possible uses. This allowed us to develop not only a precise equipment list for the hotel, but more importantly, a plan for lighting control in the conference room that would allow management to change the levels and type of light in the conference room quicker than they could change the setup.

We ended up installing a blend of fluorescent and halogen lights on multiple switching points and dimmer controls. For the bright, general lighting that would be required for trade shows, we installed 2X4 T8 fluorescents controlled by on/off switches. For indirect lighting, we installed wall sconces along the sides of the conference room. This would provide just enough lighting for AV presentations. Finally, to create a light source that would allow the conference room to be used for everything from motivational speaking to formal dining events, we installed a series of halogen recessed lights over the stage and throughout the room.

This new system now allows event coordinators to either turn all lights on at maximum capacity when high foot candle levels were required, and to turn off fluorescent lighting and precisely adjust incandescent sources and sconces to lighting levels specifically appropriate to respective functions.

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