Orgo questions

[Bigbirdo]

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1. Is it true that you can not use Fischer projection to determine if a molecule is meso because it does not represent the whole structure?

2. How many stereoisomer does a meso molecule have? 0 or 1?

3. For question 141, why isn't E a correct Newman projection?

4. For the second picture, what is the name of reaction that turn second product to the third product? I dont think I learned this before so I want to search the name and learn more.

5. For question 169, when do you use graduate cylinder and volumetric flask? I know that you use buret to deliver a known volume of acid or base and use pipet to deliver other types of liquid with known volumes. (correct me if I am wrong.)

Your guys are so awesome, thanks a lot!!

 

[KyoPhan]

1) Fischer projection DOES represent the whole structure, and it also tells you their connections relative to one another. You can also determine meso from the fischer.

2) I'm not sure if that's a valid question. To find the # of a stereoisomer, it's 2^n where n is the # of chiral carbon. If a meso compound is possible, then the # of stereoisomer is (2^n)-1.

3) edit: nm E is not a hexane like shulace said below

4) Gabriel Synthesis? Not sure.

 

[shulace]

4. It is Gabriel synthesis and the funky molecule that's involved is called phthalimide.

5. I remember getting that question wrong. Was the answer pipette?

Please correct me if I'm wrong, but volumetric flasks are used for dilutions bc they are good for 2 decimal places and are usually "nice" volumes (100 mL, 250 mL, etc).

 

[tendram]

5. Graduated cylinders are used when you need to measure a volume that does not need to be very precise. Volumetric flasks on the other hand aren't really used for measuring volume to be added to a solution, but rather to make solutions of very precise concentration (volumetric flasks are used a lot when making solutions for spectroscopic analysis where the solutions need to be of a very precise concentration). I would say that the most likely answer to this question would be a graduated cylinder since they didn't specify what kind of experiment it is and that all of the other choices are not used to measure any specific type of volume.

 

[shulace]

Sorry for double posting, but for 3)
Answer choice E is branched and is no longer hexane

 

[Bigbirdo]

4. It is Gabriel synthesis and the funky molecule that's involved is called phthalimide.

5. I remember getting that question wrong. Was the answer pipette?

Please correct me if I'm wrong, but volumetric flasks are used for dilutions bc they are good for 2 decimal places and are usually "nice" volumes (100 mL, 250 mL, etc).

The answer is pipette, so how do you decide when to use pipette and when to use volumetric flask? Is flask used as a container rather than a transferring tool?

 

[Bigbirdo]

5. Graduated cylinders are used when you need to measure a volume that does not need to be very precise. Volumetric flasks on the other hand aren't really used for measuring volume to be added to a solution, but rather to make solutions of very precise concentration (volumetric flasks are used a lot when making solutions for spectroscopic analysis where the solutions need to be of a very precise concentration). I would say that the most likely answer to this question would be a graduated cylinder since they didn't specify what kind of experiment it is and that all of the other choices are not used to measure any specific type of volume.

The answer is pipette. I am a little confused by what you said. Do you mean that a flask is used as a container rather than a transferring tool?

 

[Bigbirdo]

1) Fischer projection DOES represent the whole structure, and it also tells you their connections relative to one another. You can also determine meso from the fischer.

2) I'm not sure if that's a valid question. To find the # of a stereoisomer, it's 2^n where n is the # of chiral carbon. If a meso compound is possible, then the # of stereoisomer is (2^n)-1.

3) edit: nm E is not a hexane like shulace said below

4) Gabriel Synthesis? Not sure.

I am confused now because Chad says that Fishcer projection does not represent the whole structure. The reason he gives is that when you look at the top carbon in a Fischer projection, the bottom carbon is in the back; when you look at the bottom carbon, the top carbon is in the back. Can anyone clarify this for me?

 

[tendram]

The answer is pipette. I am a little confused by what you said. Do you mean that a flask is used as a container rather than a transferring tool?

If the answer is pipette I think they should have been more specific. There a few different pipettes used in the lab (i.e. graduated pipette, volumetric pipette, etc.) but the plain pipettes are not really used for measuring but rather adding drops of stuff. That's just my opinion based on lab experience though.

And yes, volumetric flasks are used as containers.

 

[Bigbirdo]

Can anyone tell me if Fischer projection represents the whole structure of a molecule? Chad said no, but someone here said yes, so I am confused.