Identifying chiral center

[Bananas99]

First of all I believe this should be an easy question but I honestly have never had to identify chiral centers. I just know that a chiral center is a carbon attached to 4 different groups. And I know that when two rings fuse together you should definitely look for a chiral center there. I think that you can't have a chiral center when you have a double bond? yes? no?

In this picture, I need you guys to look at ONLY step 1.
http://img132.imageshack.us/img132/9905/cholesterol.png

Question:
How many chiral center present in the reactant side and how many on the product side?

If possible can you guys label the chiral centers on the picture and post back the link to me?

thank you.

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[PiBond]

I got 7 on the reactant side and 5 on the product side. Hopefully someone can double check my answer since I'm looking at this on my iPhone and it's slightly blurry.

Remember that a chiral center is also sp3 hybridized, hence there's no double bond

 

[Bananas99]

I got 7 on the reactant side and 5 on the product side. Hopefully someone can double check my answer since I'm looking at this on my iPhone and it's slightly blurry.

Remember that a chiral center is also sp3 hybridized, hence there's no double bond

The answer is 7 on the reactant side and 6 on the product.

Can you please circle the carbons?

 

[PiBond]

We're just looking at step 1, right? The product in step 1 has 5 chiral centers, unless I missed one. However, the overall product in step 3 does have 6 chiral centers...is that what you're referring to?

I'm at work on my phone so I'm not able to circle anything at the moment. Sorry

 

[Bananas99]

We're just looking at step 1, right? The product in step 1 has 5 chiral centers, unless I missed one. However, the overall product in step 3 does have 6 chiral centers...is that what you're referring to?

I'm at work on my phone so I'm not able to circle anything at the moment. Sorry

No. I am still referring to the product for the first step. I circled all the chiral centers and I got 6. Here is the picture (I circled the chiral center in red)

http://img827.imageshack.us/i/cholesteroledited.png/

Am I right?

 

[PiBond]

No. I am still referring to the product for the first step. I circled all the chiral centers and I got 6. Here is the picture (I circled the chiral center in red)

http://img827.imageshack.us/i/cholesteroledited.png/

Am I right?

No, the 2 carbons that you circled that make up the alkene are sp2 hybridized and therefore aren't chiral centers. There's also one that you missed on the bottom left of the molecule where the -OH is attached. The other 4 that you circled are correct and leaves us with a total of 5 chiral centers.

Does that make sense?

 

[Bananas99]

No, the 2 carbons that you circled that make up the alkene are sp2 hybridized and therefore aren't chiral centers. There's also one that you missed on the bottom left of the molecule where the -OH is attached. The other 4 that you circled are correct and leaves us with a total of 5 chiral centers.

Does that make sense?

I believe that the carbon on the bottom left in which -OH group is attached isn't a chiral carbon

if you look at it the carbon makes a bond with:
1. OH
2. H
3. CH2
4. CH2

Notice that there are 2 of the same group attached to that carbon (two Ch2's). A chiral carbon must have 4 different substituent
I am not sure if I am right?

about the two carbons that you said are sp2 hybridized are you saying that you can't have a chiral center where there is a double bond?

 

[PiBond]

I believe that the carbon on the bottom left in which -OH group is attached isn't a chiral carbon

if you look at it the carbon makes a bond with:
1. OH
2. H
3. CH2
4. CH2

Notice that there are 2 of the same group attached to that carbon (two Ch2's). A chiral carbon must have 4 different substituent
I am not sure if I am right?

about the two carbons that you said are sp2 hybridized are you saying that you can't have a chiral center where there is a double bond?

It's the first point of difference when deciding if a carbon is chiral or not. Even though there's 2 CH2 groups directly attached we need to keep on going to find out if they're actually identical substituents (and we discover they're not). Therefore, it's a chiral center.

And yes, the carbon involved in the double bond cannot be a chiral center given it's hybridization and number of groups attached.

 

[Bananas99]

It's the first point of difference when deciding if a carbon is chiral or not. Even though there's 2 CH2 groups directly attached we need to keep on going to find out if they're actually identical substituents (and we discover they're not). Therefore, it's a chiral center.

And yes, the carbon involved in the double bond cannot be a chiral center given it's hybridization and number of groups attached.

I'm not sure what you mean by keep going to find out if they are identical. And they turn out to be not identical

 

[orgohacks]

I'm not sure what you mean by keep going to find out if they are identical. And they turn out to be not identical

It's a chiral center. Yes, it's attached to H, OH, and two CH2's but - you can't just stop there arbitrarily. You have to keep following the chain to see if there's a difference. If you go further you'll see that it's attached to CH2CH2- and CH2CH= . Therefore it is chiral.

You need to keep following the chain. To give an absurd example, the alcohol CH3(CH2)99CHOH-(CH2)100CH3 would have a chiral center.

 

[Bananas99]

It's a chiral center. Yes, it's attached to H, OH, and two CH2's but - you can't just stop there arbitrarily. You have to keep following the chain to see if there's a difference. If you go further you'll see that it's attached to CH2CH2- and CH2CH= . Therefore it is chiral.

keep going only around the ring?

 

[WhiteWashed]

It's a chiral center. Yes, it's attached to H, OH, and two CH2's but - you can't just stop there arbitrarily. You have to keep following the chain to see if there's a difference. If you go further you'll see that it's attached to CH2CH2- and CH2CH= . Therefore it is chiral.

keep going only around the ring?

sooo do we have a consensus that there are only 5 chiral carbons in the product of step 1?

sp2=never chiral....or is my whole world upside down???

 

[Longshanks]

sooo do we have a consensus that there are only 5 chiral carbons in the product of step 1?

sp2=never chiral....or is my whole world upside down???

sp2 can not be chiral as the carbon is unable to be bound to four different groups. so you are correct there.

 

[WhiteWashed]

sp2 can not be chiral as the carbon is unable to be bound to four different groups. so you are correct there.

sooo only 5 chiral carbons in the product of step 1?

 

[Bananas99]

sooo do we have a consensus that there are only 5 chiral carbons in the product of step 1?

sp2=never chiral....or is my whole world upside down???

I think so.

So let say I want to practice identifying chiral centers. for step number 3 the reactant has 4 chiral centers?
I circled them in red

http://img403.imageshack.us/img403/7672/practice.png

So things to look for when finding chiral centers:
1. No double bond
2. Substituent sticking out
3. Ring fuse

am I right?

Man I feel so dumb..

 

[WhiteWashed]

I think so.

So let say I want to practice identifying chiral centers. for step number 3 the reactant has 4 chiral centers?
I circled them in red

http://img403.imageshack.us/img403/7672/practice.png

So things to look for when finding chiral centers:
1. No double bond
2. Substituent sticking out
3. Ring fuse

am I right?

Man I feel so dumb..

you're missing 1 more...no need to feel dumb. This is just stuff you haven't mastered. Keep working hard and you can get it.

 

[LaurenMCAT]

I think so.

So let say I want to practice identifying chiral centers. for step number 3 the reactant has 4 chiral centers?
I circled them in red

http://img403.imageshack.us/img403/7672/practice.png

So things to look for when finding chiral centers:
1. No double bond
2. Substituent sticking out
3. Ring fuse

am I right?

Man I feel so dumb..

Don't feel dumb! This stuff CAN be hard...and it's awesome that you're actively looking for help and working to understand it...not just pushing it aside

To add my two cents, in ...
Step 1:
reactant - 7 chiral centers
product - 5 chiral centers
Step 3:
reactant - 5 chiral centers
product - 6 chiral centers

The one chiral center you missed in the Step 3 reactant is the ring-bound carbon of the cyclopentane that has a bond coming out of the page to connect the long alkyl substituent. (You DID correctly circle the chiral carbon of that long alkyl group - the top most red circle on the compound!)

You correctly identified all the others!

I hope what I wrote makes sense...hahhaa...

 

[Bananas99]

you're missing 1 more...no need to feel dumb. This is just stuff you haven't mastered. Keep working hard and you can get it.

The ones I circled are correct though right?

is this the remaining one? I circled in blue
http://img291.imageshack.us/img291/949/practiceu.png

by the way I posted this without looking at the answer that lauren posted

So you these are the things you look for:
1. no double bond
2. ring fuse
3. carbon that is attached to some kind of substituent.

Am I correct?

Honestly I have never even heard of the word "chiral" and I have taken all my chemistry except orgo II.

 

[LaurenMCAT]

The ones I circled are correct though right?

is this the remaining one? I circled in blue
http://img291.imageshack.us/img291/949/practiceu.png

by the way I posted this without looking at the answer that lauren posted

So you these are the things you look for:
1. no double bond
2. ring fuse
3. carbon that is attached to some kind of substituent.

Am I correct?

Honestly I have never even heard of the word "chiral" and I have taken all my chemistry except orgo II.

YOU GOT IT!!!

(Let me tell you how much the word "chiral" used to scare me...then, like you, I just practiced practiced practiced! Keep it up!)

 

[Bananas99]

YOU GOT IT!!!

(Let me tell you how much the word "chiral" used to scare me...then, like you, I just practiced practiced practiced! Keep it up!)

Gracias senora.

So I am going to try to circle the chiral center of the reactant in step one

is this right
http://img32.imageshack.us/img32/7371/cholesterol999.png

 

[Bananas99]

Did I correctly circle the chiral centers in reactant of step 1?

 

[LaurenMCAT]

Did I correctly circle the chiral centers in reactant of step 1?

You did!

 

[Bananas99]

You did!

Yesssssss...

Lauren, you have been really helpful so far. Do you mind if I add you ass a friend and ask you questions in the future maybe?

 

[Reaction]

First of all I believe this should be an easy question but I honestly have never had to identify chiral centers. I just know that a chiral center is a carbon attached to 4 different groups. And I know that when two rings fuse together you should definitely look for a chiral center there. I think that you can't have a chiral center when you have a double bond? yes? no?

In this picture, I need you guys to look at ONLY step 1.
http://img132.imageshack.us/img132/9905/cholesterol.png

Question:
How many chiral center present in the reactant side and how many on the product side?

If possible can you guys label the chiral centers on the picture and post back the link to me?

thank you.

You are right that you can't have a chirality center with a double bond or triple bond because the carbon is attached to something twice or three times. I think there are 7 Chirality centers on the Reactant side and 5 Chirality centers on the product side

PiBond is correct=]

Sorry I don't know how to label it=/

 

[LaurenMCAT]

Yesssssss...

Lauren, you have been really helpful so far. Do you mind if I add you as a friend and ask you questions in the future maybe?

For sure!

But...can we also post your questions publicly so that everyone can benefit? I bet a lot of other people have the same questions you do

 

[Bananas99]

for sure!

But...can we also post your questions publicly so that everyone can benefit? I bet a lot of other people have the same questions you do

of course.