quick test questions, thanks!

[mgdent]

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1. Is NH3 e- withdrawing or donating? NH2 is e donating but I wasnt sure about NH3.

2. For the NMR of CH3-CO-CH2-CH3 is this correct? 1 quartet, 1 singlet, 1 triplet? For the 2 methyl groups, would you see 2 quartets or 1? What distinguishes them from each other and indicates the presence of 2 methyl groups?

3. I'm getting a little confused with racemic structures. For instance, the following are racemic.
CHO
H--OH
OH--H
CHO

and

CHO
OH-H
H-OH
CHO


Now what confuses me is the following are enantionmers.

H
HO--CH3
HO--CH2CH3
H

H
CH3-OH
CH2CH3-OH
H

To me these look the same.. What am I missing here? They both look like they can be rotated and are the same.

4. I'm throwing a math problem in here lol..It was from the ADA sample test and I think there might be a mistake in the answer key..

Find the average of the following list of
three weights: 3 lb. 2oz., 4 lb. 6 oz., and
9 lb. 10 oz.

A. 5 lb. 6 oz.
B. 5 lb. 6 1/3 oz.
C. 5 lb. 11 1/3 oz.
D. 5 lb. 39 1/3 oz.
E. 8 lb. 9 oz.

It says the answer is C but I'm not getting it. There are 16 oz in a lb so (3*16)+(2)+(4*16)+(6)+(9*16)+(10)= 274 divided by 3 = 91.33 divided by 16 = 5 lb 7 oz. Any suggestions? Thanks guys.


Again, I REALLY appreciate everyones input. It means a lot.

 

[TriCuspid]

1. Is NH3 e- withdrawing or donating? NH2 is e donating but I wasnt sure about NH3.

NH3 is e- withdrawing, deactivating, and meta director.

2. For the NMR of CH3-CO-CH2-CH3 is this correct? 1 quartet, 1 singlet, 1 triplet?

1 singlet, 1 quartet, 1 triplet

For the 2 methyl groups, would you see 2 quartets or 1? What distinguishes them from each other and indicates the presence of 2 methyl groups?

Huh?


3. I'm getting a little confused with racemic structures. For instance, the following are racemic.
CHO
H--OH
OH--H
CHO

and

CHO
OH-H
H-OH
CHO

"In chemistry, a racemic mixture, or racemate, is one that has equal amounts of left and right-handed enantiomers of a chiral molecule" -wikipedia. These are enantiomers.. R/S... so... Yeah. its racemic

Now what confuses me is the following are enantionmers.

H
HO--CH3
HO--CH2CH3
H

H
CH3-OH
CH2CH3-OH
H

To me these look the same.. What am I missing here? They both look like they can be rotated and are the same.

Assuming you meant:
H
HO- C -CH3
HO- C -CH2CH3
H

H
CH3- C -OH
CH2CH3- c -OH
H

Enantionmers

4. I'm throwing a math problem in here lol..It was from the ADA sample test and I think there might be a mistake in the answer key..

Find the average of the following list of
three weights: 3 lb. 2oz., 4 lb. 6 oz., and
9 lb. 10 oz.

A. 5 lb. 6 oz.
B. 5 lb. 6 1/3 oz.
C. 5 lb. 11 1/3 oz.
D. 5 lb. 39 1/3 oz.
E. 8 lb. 9 oz.

It says the answer is C but I'm not getting it. There are 16 oz in a lb so (3*16)+(2)+(4*16)+(6)+(9*16)+(10)= 274 divided by 3 = 91.33 divided by 16 = 5 lb 7 oz. Any suggestions? Thanks guys.

80oz= 5lbs that leaves 11.33 oz left. so thats 5lbs 11 1.3 oz

 

[herkulease]

1. Nh3 is withdrawing.
2. you should see 1 quartet, 1 singlet, and 1 triplet.
3. I'll have to draw those out and I'll update you post when I do that.
4. Your math is wrong.

you are correct the total is 274 oz and the average is 91.33 oz for each piece of meat.

But you when divided by 16 oz. the answer is 5.68 pounds. Not 5 pounds and 7 oz.

5 * 16 oz = 80 oz

91.33 - 80 = 11.3 oz left.

thus C. 5 lbs and 11 1/3 oz.

 

[ArmyPilot]

Please someone correct me if Im wrong, its 0430 where Im at and Im half awake.

1. Is NH3 e- withdrawing or donating? NH2 is e donating but I wasnt sure about NH3. -------> in reference to aromatics, it is e- withdrawing as there is a + charge on the NH3


2. For the NMR of CH3-CO-CH2-CH3 is this correct? 1 quartet, 1 singlet, 1 triplet? For the 2 methyl groups, would you see 2 quartets or 1? What distinguishes them from each other and indicates the presence of 2 methyl groups? sorry, no comment as I have avoid the spectro stuff until I get closer to the DAT

3. I'm getting a little confused with racemic structures. For instance, the following are racemic.
CHO
H--OH --->> r configuration
OH--H --->> r configuration
CHO

and

CHO
OH-H --->> s configuration
H-OH --->> s configuration
CHO
--these are racemixtures because they are both exactly the opposite configurations (enantiomers)
-if they were, say RS and the other was SR, they would be a racemic once again as they are enantiomers.
--If one was, say RR and the other RS, they would diastomers (spelling is off) because they different at exactly one charilty center

Now what confuses me is the following are enantionmers.

H
HO--CH3 --->> s configuration
HO--CH2CH3 --->> R configuration
H

H
CH3-OH --->> R configuration
CH2CH3-OH --->> S configuration
H

To me these look the same.. What am I missing here? They both look like they can be rotated and are the same.
-See previous response: RS config and SR config are the exact opposite, hence entantiomer



4. I'm throwing a math problem in here lol..It was from the ADA sample test and I think there might be a mistake in the answer key..

Find the average of the following list of
three weights: 3 lb. 2oz., 4 lb. 6 oz., and
9 lb. 10 oz.

A. 5 lb. 6 oz.
B. 5 lb. 6 1/3 oz.
C. 5 lb. 11 1/3 oz.
D. 5 lb. 39 1/3 oz.
E. 8 lb. 9 oz.

It says the answer is C but I'm not getting it. There are 16 oz in a lb so (3*16)+(2)+(4*16)+(6)+(9*16)+(10)= 274 divided by 3 = 91.33 divided by 16 = 5 lb 7 oz. Any suggestions? Thanks guys.
- your error is in your units; you did all that division to get 5.7 - you are still in pounds, meaning 5.7 pounds. you have one more step to go; .7 X 16 ounces = 11 1/3 ounces;


Again, I REALLY appreciate everyones input. It means a lot.

good luck bro; slow down when you are doing these problems - I have a habit of rushing too and it only bites you in the rear.

 

[mgdent]

thanks a lot man, that was really helpful. just one thing- so essentially are racemic mixtures the same as the 2 given enantiomers. basically, would they show us both those structures and say are they a. enantiomers b. racemic etc no right because it could be both answers? sorry if that makes no sense haha getting tired here too

 

[mgdent]

does that last post i made make sense?

 

[DQLEUCD]

Please someone correct me if Im wrong, its 0430 where Im at and Im half awake.

1. Is NH3 e- withdrawing or donating? NH2 is e donating but I wasnt sure about NH3. -------> in reference to aromatics, it is e- withdrawing as there is a + charge on the NH3


2. For the NMR of CH3-CO-CH2-CH3 is this correct? 1 quartet, 1 singlet, 1 triplet? For the 2 methyl groups, would you see 2 quartets or 1? What distinguishes them from each other and indicates the presence of 2 methyl groups? sorry, no comment as I have avoid the spectro stuff until I get closer to the DAT

3. I'm getting a little confused with racemic structures. For instance, the following are racemic.
CHO
H--OH --->> r configuration
OH--H --->> r configuration
CHO

and

CHO
OH-H --->> s configuration
H-OH --->> s configuration
CHO
--these are racemixtures because they are both exactly the opposite configurations (enantiomers)
-if they were, say RS and the other was SR, they would be a racemic once again as they are enantiomers.
--If one was, say RR and the other RS, they would diastomers (spelling is off) because they different at exactly one charilty center

Now what confuses me is the following are enantionmers.

H
HO--CH3 --->> s configuration
HO--CH2CH3 --->> R configuration
H

H
CH3-OH --->> R configuration
CH2CH3-OH --->> S configuration
H

To me these look the same.. What am I missing here? They both look like they can be rotated and are the same.
-See previous response: RS config and SR config are the exact opposite, hence entantiomer



4. I'm throwing a math problem in here lol..It was from the ADA sample test and I think there might be a mistake in the answer key..

Find the average of the following list of
three weights: 3 lb. 2oz., 4 lb. 6 oz., and
9 lb. 10 oz.

A. 5 lb. 6 oz.
B. 5 lb. 6 1/3 oz.
C. 5 lb. 11 1/3 oz.
D. 5 lb. 39 1/3 oz.
E. 8 lb. 9 oz.

It says the answer is C but I'm not getting it. There are 16 oz in a lb so (3*16)+(2)+(4*16)+(6)+(9*16)+(10)= 274 divided by 3 = 91.33 divided by 16 = 5 lb 7 oz. Any suggestions? Thanks guys.
- your error is in your units; you did all that division to get 5.7 - you are still in pounds, meaning 5.7 pounds. you have one more step to go; .7 X 16 ounces = 11 1/3 ounces;


Again, I REALLY appreciate everyones input. It means a lot.

good luck bro; slow down when you are doing these problems - I have a habit of rushing too and it only bites you in the rear.

Everything looks great. For the math, a faster approach would be to convert everything into ounces and solve. Then convert your answer back to lbs and ounce.