Refers to the spatial arrangement of atoms in a chemical entity.

learn more… | top users | synonyms (1)

1
vote
1answer
24 views

Propene react with ICl

When propene react with ICl , it gives an inoptically active compound ,why. According to me there is chiral carbon so it should be optically active
4
votes
1answer
39 views

Stereoselectivity of hydroboration

The above compound undergoes hydroboration. I originally thought that the $\ce{OH}$ group can attach to any of the 2 carbons plus there are 2 possible enantiomers at each position. So there should ...
0
votes
1answer
24 views

Possible E2 products of S-2-bromo-2-methyl-1-phenylbutane

I have been asked to predict wether the following reaction will proceed by elimination or substitution. $\hspace{2.4cm}$ I believe that the reaction would proceed by the $\mathrm{E2}$ mechanism. I ...
3
votes
1answer
40 views

Clarification needed - Number of stereoisomers

How many stereoisomers are possible for the compound in the picture? I tried to draw a rough picture and indicated the chiral carbons. I'm getting 8 stereoisomers are possible but my book gives the ...
3
votes
1answer
71 views

Stereospecific in SN2 reaction

(S)-1-bromo-1-fluoroethane reacts with sodium methoxide to give pure (S)-1-fluoro-1-methoxyethane. This is an SN2 reaction so inversion should take place , hence the product should be R but it is not ...
4
votes
1answer
87 views

Which groups take priority when predicting the stereochemical outcome of addition to cyclohexenes?

I am trying to understand the stereochemistry of iodolactonisation of this cyclohexene. When the iodine reacts forming the iodonium ion, I can't work out if it would attack from the top or the bottom? ...
7
votes
2answers
308 views

How do atoms with 3 different covalently bonded substituents and one electron pair behave?

If one has a carbon atom with 4 different groups covalently bonded to it, it is called asymmetric and there can be enantiomers etc. But imagine if one has a different central atom, for example a ...
3
votes
0answers
15 views

Steric hindrance of an unbonded electron pair

This question is half inspired by this question, and half inspired by the structure of molecules like hydrazine and hydrogen peroxide. When I was looking at the aforementioned molecules, I started ...
8
votes
1answer
78 views

How much steric hindrance does a phenyl group offer?

I've come across a question in my revision in which I am asked to compare the steric hindrance provided by a number of substituents. Those relating to phenyl are ranked relatively low, despite it ...
-1
votes
0answers
25 views

Enantiomers or identical compounds

There are two compounds I have seen in a organic book (Solomons) in that it is written both compounds are identical. But according to me it is not, compound B should have S configuration, but in it is ...
1
vote
1answer
21 views

What is the absolute configuration of carbon 4 in glucopyranose?

My colleague and I have been wrestling with the assignment of chirality to the 4th carbon atom in glucopyranose. In the linear form of glucose, the 4th carbon is definitely (R); therefore it will ...
9
votes
3answers
326 views

Difference between Epimers and Diastereomers

My lecture notes describe epimers as compounds which differ by configuration at only one carbon and gives the example of D-erythrose and D-threose as being epimers. However isn't that the same thing ...
0
votes
0answers
13 views

Chirality of carbon and R/S naming when enatiomeric groups attached [duplicate]

when checking chirality for a tetrahedral, let's take carbon as an example, will two enantiomers or diastereomes of a group attached to same carbon cause chirality at that carbon, I mean are they ...
2
votes
1answer
24 views

Why are the ethyl ester methylene protons not diastereotopic in ethyl (+-)-2-methylbutyrate?

In the following compound, there is one chiral center and two methylene groups. Why are the protons on the ethyl ester methylene not diastereotopic?
3
votes
2answers
100 views

Is axis of symmetry considered a true symmetry?

In most of the books when i read about optical activity of a compound this is what they say: A compound that does not posses any kind of symmetry is optically active. In other words chiral compounds ...
0
votes
1answer
22 views

Why is there syn-addition in this example?

In my book I read that halogenation of alkenes results in anti-addition. Is this example showing syn-addition? The example:
6
votes
1answer
51 views

Stereoselectivity differences in Lindlar's catalyst and Na/NH3?

Why does using the Lindlar's catalyst form cis-alkenes whereas $\ce{Na/NH3}$ forms trans-alkenes?
3
votes
1answer
40 views

l- versus d-glucose

I recently purchased Dextrose from a local bulkfood store. I want to use it instead of table sugar. My concern is that it may be l-glucose instead of d-glucose. According to Wikipedia l-glucose is too ...
3
votes
1answer
42 views

Are labile tetrahedral [Mabcd] complexes optically active?

In the above mentioned complex, there is a chiral centre at the metal, and hence it seems the compound must be optically active. But my course notes say that the ligands keep on changing their their ...
1
vote
1answer
36 views

Why does (3E)-3,4-dimethylhex-3-ene yield a meso dihalide when reacted with Br2/CCl4 at room temperature?

The answer is B. But why? What makes it so different than the others? I know that it attacks from the back (anti addition). But can't it do that for all and result in a meso compound?
0
votes
1answer
34 views

Physical properties of geometric isomers

I've learnt that cis isomers have higher boiling point than the trans ones. Why does not that rule apply on Fumaric and maleic acids?
0
votes
1answer
47 views

Are these three molecules optical isomers?

In the structures below (2) vs (3) seem obvious optical isomers to me. But what about (1)? Is that just a stuctural isomer (e.g. Butane vs Isobutane) or is there a more specific way to describe the ...
-4
votes
2answers
33 views

Hands and chirality [duplicate]

I was told by my teacher that human hands are the best examples of chirality as both the hands are mirror images of each other but cannot be superimposed on each other. My question is if we join ...
1
vote
0answers
25 views

Draw a structure for each of the following isomers of unsaturated amine 1

My ochem professor has several practice exams as resources but does not include answers, I believe I understand the concepts but once I apply them I'm not sure whether I'm right or clueless. Can ...
1
vote
1answer
38 views

Chair conformation chirality

I have two questions regarding this solution: I can't see how the structure drawn is the enantiomer. How do I rotate the ring inversion chair form to obtain the enantiomer?
2
votes
2answers
99 views

DL vs dl notation

As the L-isomer of glucose, it is the enantiomer of the more common D-glucose. Source: Wikipedia As far as I know enantiomers or Optical isomers are non superimposable mirror image structures ...
1
vote
1answer
39 views

Why is this stereocenter by the Br an R? I thought it was S?

Why is this stereocenter by the Br an R? I thought it was S? For problem b in the following image:
1
vote
0answers
17 views

Number of stereo-isomeric products?

This is the question:- And this is my approach:- As you can see, according to my solution, the answer should be 2. But the answer is 4. Also, I have doubt in the first step that whether the anion ...
1
vote
1answer
35 views

Can diastereomers form a racemic mixture?

In my book, it says racemic mixture is the mixture of + and - optical isomers and it is optically inactive. This means enantiomers (optical isomers which are mirror images to each other) can form ...
0
votes
0answers
33 views

Cahn-Ingold-Prelog priority: how to 'unfold' this hypothetical group?

Considering this hypothetical functional group (totally not chemically relevant), how would one 'unfold' it in order to determine its priority? Is what I am proposing correct?
2
votes
2answers
75 views

Stereochemistry in Sn2 reaction

I'm confused why the absolute configuration always has to change after an $S_N2$ reaction: For example, in primary alkyl halide above there are 4 planes Nu can attack; and absolute configuration is ...
1
vote
0answers
25 views

(stereochemistry)epoxide from alkene

picture above describes two ways of forming epoxides from alkene. (a) peroxy acid (b) Br2 and H2O / NaOH it says R groups stay in the same position. and I want to ask some about (b). is it ...
1
vote
0answers
14 views

How do you use valences in the chemical equations? [closed]

Can anyone give me tips on how to solve and balance chemical equations using valences and periodic table ?
2
votes
0answers
27 views

Effect of Steric Environment on Selectivity of Protection by Sisyl Chlorides

(sorry about the poor diagram. I don't know how to add in the arrows and stuff) Draw the product when the following compound is reacted with sisyl chloride in the presense of DMF catalyst at ...
5
votes
1answer
108 views

Identifying Chiral Carbons

Looking at this structure, I would say this molecule has five chiral carbons. However, its IUPAC name (3R,4R,5S,6R)-3-amino-6-(hydroxymethyl)oxane-2,4,5-triol suggests that there are only four. Which ...
4
votes
1answer
87 views

Find the number of stereoisomers

Find the number of stereoisomers of the following compound: I chose the answer is $16$ or option (1). The double bond in the ring cannot show geometrical isomerism. The first double bond on the ...
0
votes
0answers
23 views

While finding out chiral centers should lone pair be considered as a group? [duplicate]

My book says it is a chiral center. Should I count lone pairs as one of the groups while finding chiral center ?
1
vote
1answer
61 views

R or S configuration

what is the specific configuration (R or S) of this compound ?
9
votes
1answer
107 views

Mechanism of substitution reaction with no change in stereochemistry

When (2​S,3​R)-3-iodobutan-2-ol undergoes a substitution reaction with sodium azide the only organic product from the reaction is (2​S,3​R)-3-azidobutan-2-ol. Give a mechanism for the reaction. ...
0
votes
0answers
41 views

SN2 reaction and Absolute Configuration (R/S)

I know that an $\mathrm{S_N2}$ reaction proceeds through complete inversion of configuration, but is it necessary that the Absolute Configuration (R/S) of the chiral centre changes after an ...
1
vote
0answers
22 views

Optically active [closed]

In the following compounds , how can we say that both are are optically active . According to me they both do not have chiral carbon , then how can we say that both are chiral .
1
vote
1answer
46 views

Isomers of co-ordination compounds

Does $\ce{[Co(H2O)3Br3]}$ show geometrical and optical isomerism? According to me $\ce{Co}$ should be $\mathrm{sp^3d^2}$ hybridised giving an octahedral geometry. It is of the form $\ce{Ma3b3}$ type. ...
3
votes
1answer
130 views

Is it true that human cells grow in levorotation?

I remember reading this in a popular science magazine, some 20 years ago: that in most of the living organisms, the proteins (in fact, the amino acid molecules that make the proteins) are levorotatory ...
2
votes
1answer
71 views

Optical isomerism regarding diastereomers

Are diasteriomers always optically active? If not then why? Though they are chiral then also.
4
votes
1answer
440 views

What is the difference between D and L configuration, and + and -?

What is the difference between D and L configuration, and + and -? My textbook says they are two different things. It also says that the correct way to name glucose is D(+)-glucose. Could someone ...
1
vote
0answers
41 views

isomerism in coordination complexes

Is there any difference between geometrical and cis-trans isomerism in coordination complexes, because in my book it is given that complexes of the form [Ma4bc] does not show cis-trans isomerism but ...
0
votes
0answers
28 views

Why does a compound need to have a Hydrogen attached to the Carbon, in order for the racemization to happen with the help of a base?

Acids and Bases accelerate the enolisation process, and help also the racemisation process. But, in the compounds that don't contain a hydrogen atom attached to the chiral carbon, for example ...
6
votes
0answers
81 views

Masamune's rule of diastereoselectivity multiplicity

In a reaction between a chiral substrate and chiral reagent, their asymmetric inductions could cooperate (matched pairs) or compete (mismatched pair). According to Masamune, in a matched pair the ...
0
votes
1answer
117 views

Examples from everyday life for diastereoisomers ?

Like the amino-acids and sugars that are enantiomers, can you give any examples of diastereoisomers ? where can we find them in everyday life ?
0
votes
0answers
27 views

Are isomers and stereoisomers the same thing?

I am doing a presentation regarding Stereochemistry, and I am a little confused with the terminology. My question is: Are isomers and stereoisomers the same thing? Do they differ from each other?