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

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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....
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1answer
44 views

Do compounds show geometric isomerism if the double bond is delocalized?

Pent-3-en-1-yne ($\ce{CH3-CH=CH-C#CH}$) has a double bond and triple bond delocalizing. Does it show cis-trans isomerism?
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94 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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38 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. ...
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141 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?
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36 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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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
160 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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291 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 ...
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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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96 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 ...
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24 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 ...
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34 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 ...
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2answers
78 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 ...
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1answer
40 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
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1answer
43 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 ...
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1answer
26 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
88 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 ...
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93 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? ...
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3answers
319 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 ...
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0answers
17 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
93 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 ...
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1answer
22 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
428 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 ...
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0answers
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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
30 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?
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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
42 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:
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1answer
61 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
51 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
50 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 ...
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1answer
44 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?
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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?
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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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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 ...
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0answers
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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 ...
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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?
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2answers
143 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 ...
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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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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 ...
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1answer
71 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 ...
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34 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
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2answers
80 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 ...
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(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 possible ...
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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 ?
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28 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 $-10\ ...
5
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1answer
109 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 ...
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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 ...
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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 ?