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

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hydrolysis of chlorocyclopropane rings [on hold]

Why is the hydrolysis of trans-2,3-dimethyl-1-chlorocyclopropane more rapid than for the cis-isomer List item cis-isomer?
4
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2answers
51 views

Cis/trans stereochemistry dictating pKa

Why is trans-4-phenylcyclohexane-1-carboxylic acid a stronger acid than the cis isomer? In the cis-isomer the carboxyl group is axial; and, given the 1,4 distance from the phenyl, why would ...
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32 views

Asymmetric hydroboration [on hold]

How to predict the stereochemistry of asymmetric hydroboration? Example is given below.
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1answer
66 views

Why are substituted biphenyls optically active?

Why are some substituted biphenyl compounds optically active and what kind of substituted biphenyls are optically active . I read this in a book but no satisfactory reasons were given and no examples ...
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18 views

how can we decide 'R' or 'S' configuration for sp2 hybridised carbon such as in But-2-ene the second and third carbons are chiral centres [closed]

In this you can choose any 3-D arrangement as you like just show me what you chose and how you did it
6
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1answer
59 views

Diastereoselectivity in synthesis problem (4 stereocenters)

Why is the particular diastereomer the major product of the sequence starting from racemic enone? I know that hydroboration is syn, therefore the arrangement of ring junction H atom and OH group. Why ...
3
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2answers
64 views

Can a system of 2 consecutive Biphenyl systems be optically active , even if any adjacent biphenyl systems arent optically active?

This question came in an online test, where they asked whether or not 22,26-dibromo-12,32-dichloro-23,25-diiodo-16,36-dimethyl-11,21:24,31-terphenyl was optically active. (The answer is that it is ...
4
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1answer
59 views

Trans-hydrogenation of alkenes

Both this and that question seem to indicate that the hydrogenation of alkenes to alkanes or alkynes to alkenes is always a syn process. However since hydrogenation is not a concerted process, I do ...
7
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1answer
75 views

Achiral universe - asymmetric synthesis

Would it be somehow possible to conduct asymmetric synthesis if all chiral molecules would exist only as racemates in nature?
4
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1answer
28 views

Are all concerted electrophilic addition reactions of alkenes syn?

The Organic Chemistry book I am using (8th edition Carey, et al.) doesn't say it straight out, but I am wondering if it's a universal rule that all concerted electrophilic additions of alkenes are syn....
11
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1answer
97 views

Molecular knots absolute configuration

How is the absolute configuration of chiral molecular knots determined? What rules should be applied? For centrochiral compounds, the CIP rules are applied, for axially chiral is described here and ...
4
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1answer
43 views

1,2,3-Trimethylcyclopropane stereoisomers

1,2,3-Trimethylcyclopropane has two stereoisomers. When one of the methyl groups is above the plane and other two are below the plane, then there are two chiral centres as well as a plane of symmetry. ...
6
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1answer
149 views

Axial Chirality in Carbodiimides

Do carbodiimides exhibit axial chirality or do the nitrogens invert rapidly enough, as in trisubstituted amines with different alkyl groups?
3
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1answer
51 views

Pinacol pinacolone rearrangement

I was reading the topic alcohol in that I saw a reaction Pinacol pinacolone rearrangement . But I am not able to find the sterochemistry of the reaction . Can anyone please tell me the ...
6
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1answer
86 views

Is these a pair of diastereomer or identical compound?

I attempted on this question (e) and found out that they are diastereomers, but the answer from the book is that they are identical. I worked out the configuration at each of the centres for the ...
10
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1answer
164 views

Can you have a meta stereocenter?

Imagine a compound such as 1,3-dibromo-1,2,3-trichloropropane. Since the first and third carbons are attached to four different groups, they are both chiral centers. Assuming that both of these ...
10
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1answer
297 views

When is Phosphorous a Stereocenter

My textbook says that in the above diagram that there is only 2 stereoisomers. I am guessing this is due to the stereogenic carbon atom and not due to the phosphorous atom which apparently isn't a ...
1
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1answer
52 views

Number of stereoisomers of 3-ethyl-1-pentene-1,4-diol

I am trying to figure out how many stereoisomers this compound has. I know that there are two chiral carbon atoms, which allow $2\times2 = 4$ possible isomers. There is also a double bond which, as ...
8
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1answer
97 views

Stereochemistry of cyclic hemiketal formation

$\hspace{5cm}$ I know that the acid protonates the carbonyl oxygen and this opens a pathway to an intramolecular cyclization reaction because the $\ce{-OH}$ group will attack the carbonyl carbon and ...
1
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26 views

Stereochemistry and epoxide opening

An alkene is reacted with a peroxyacid. Am I correct in thinking that these two different products can be obtained? I know that Gilman reagents can open epoxides, and do so on the less-substituted ...
0
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1answer
48 views

What is the result of this elimination reaction?

$$\ce{(R)-2-Bromooctane + alcoholic~KOH -> E2~reaction}$$ My answer is that this reaction will have a minor and a major product. In relation to the regiochemistry, the major product is the one ...
3
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2answers
81 views

Possible Products in the Addition To a Double Bond in a Ring

I don't understand why both these products should be different. I know hydrogenation is syn addition and both the hydrogens add from the same side, but why should the plane in which both the hydrogen ...
1
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1answer
45 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
5
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1answer
44 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 be ...
0
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1answer
28 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
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1answer
45 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
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1answer
92 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
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1answer
95 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
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3answers
320 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 ...
4
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0answers
18 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
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1answer
104 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
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1answer
25 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
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3answers
539 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
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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
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1answer
32 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
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2answers
161 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 ...
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2answers
47 views

Why is there syn-addition in this bromination of an alkene?

In my book I read that halogenation of alkenes results in anti-addition. Is this example showing syn-addition? The example:
8
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1answer
62 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
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1answer
55 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
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1answer
52 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
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1answer
46 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
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1answer
59 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
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1answer
50 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 ...
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2answers
43 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
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27 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 ...
2
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1answer
42 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
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2answers
178 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 with ...
1
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1answer
40 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:
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21 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
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1answer
93 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 ...