23
votes
Accepted
What is the role of ammonium chloride in the workup of a Grignard reaction?
Ammonium chloride ($\ce{NH4Cl}$) is the work-up reagent that quenches the magnesium alkoxide product of the Grignard addition. It is the reagent of choice as it is a proton source without being acidic;...
- 21.6k
19
votes
Accepted
Ring contraction when cyclohexene oxide is treated with methyl Grignard
Sara Jane: Lest you miss the point of the stimulating discussion between Waylander and Zhe, I would like to sum up their thoughts with a diagram. Your first clue should have been the opening line: "...
- 16.4k
16
votes
Accepted
Are there any significant uses of the compound formed by magnesium and anthracene?
It seems like an idea of using magnesium anthracene systems for the $\ce{MgH2}$ production persisted since 1980s [1] till late 2000s, when new more efficient method with better scalability for ...
- 37.4k
14
votes
Why are the products of Grignard reaction on an alpha-chiral ketone diastereomers rather than a racemate?
First of all, welcome to ChemSE on your first post. Allow me to expand on the Comment of Karsten Theis and provide you with an illustration. If a compound is racemic and bears a single stereocenter, ...
- 16.4k
12
votes
Accepted
Can Mg/ether reduce carbonyl groups?
It is known that $\ce{Mg}$ will reduce ketones. The articles (Ref.1 and 2) in the References section confirm this fact.
If you want to form the Grignard reagent of a molecule that also happens to ...
- 21.6k
11
votes
Accepted
Why do Grignard reagents add to propargyl alcohols?
The addition of Grignards to propargyl alcohols occurs via the alkoxide salt, after deprotonation:[1]
Here:
the reactivity may be explained by the stabilising influence of complexation;
the ...
- 71.1k
11
votes
Why don’t Grignard reagants react with their alcohol products?
The addition of a Grignard to a carbonyl doesn't form an alcohol—not directly at least. It forms an alkoxide ion (i.e. the conjugate base of an alcohol).
Only when that reaction is complete, is water (...
- 71.1k
10
votes
Accepted
Preparation of an aromatic Grignard reagent
I have prepared many aryl Grignards in my career. Generally the aryl bromide or iodide is easier than the chloride, but it can be done. THF is certainly fine for this, run under inert atmosphere, of ...
- 21.6k
10
votes
Reaction of Grignard reagent with primary amines
Here's the thing about Grignard reagents. Though we typically want them to do nucleophilic addition to something, these powerful bases tend to go for protons -- a faster reaction -- if there is just ...
- 53.2k
10
votes
Accepted
Why do Grignard reagents act as sources of nucleophilic R− and not Br−?
In all likelihood the halide ion does attack the substrate. But, the product such a reaction mode would form does not accumulate whereas the alkylated product does.
Recall that in a nucleophilic ...
- 53.2k
9
votes
Accepted
Rearrangement of Grignard reagent formed from exocycloproyl vinyl bromide
Grignard reagents are capable of rearranging, especially in this situation where there is significant strain. The specific vinyl bromide you drew here has been studied: J. Org. Chem., 1974, 39 (10), ...
- 969
9
votes
Is HMgX also a Grignard Reagent like RMgX?
According to Ashby and Goel [1,2] $\ce{HMgX}$ compounds are a thing. You can't make them with magnesium +$\ce{HX}$, of course (what actually happens?), but you can get them from magnesium halide ...
- 53.2k
9
votes
Accepted
Grignard reagent with sulfur dioxide
You get sulfinic acids $\ce{RSO2H}.$
This paper by Dowson et al. [1] states that Grignard plus $\ce{SO2}$ gives sulfinic acids and as a reference quotes an older article by Allen Jr. et al. [2] which ...
- 21.6k
9
votes
Accepted
Does Grignard reagent on reaction with PbCl2 give PbR4 and not PbR2?
More is involved here than the simple nucleophilic exchange normally associated with Grignard reagents. Essentially, the proposed dialkyl lead disproportionates with displacement of metallic lead. ...
- 53.2k
8
votes
Synthesis of (1S,2S,4S)-4-ethenyl-5-methylcyclohexane-1,2-diol
Because the target structure contains the motif of a cyclohexane-1,2-diol, I suggest an approach including a Diels-Alder reaction (DA in the illustration below) of 1,3-butadiene and the commercially ...
- 28.4k
8
votes
Can primary amine be produced using Grignard reagent?
Grignard reagents, in addition to being nucleophiles, are strong bases. Attempting to react a Grignard $\ce{RMgX}$ with nitrous acid is simply going to result in protonation of the Grignard to give $\...
- 21.6k
7
votes
Does Grignard reagent react with oxygen?
This paper says it does and notes that while the yield of alcohols from aliphatic Grignards is 60-90%, formation of phenols is much less satisfactory. Other methods exist for the formation of phenols ...
- 21.6k
7
votes
Accepted
Conversion from t-butanol to alkene
t-butanol + allyltrimethylsilane + Lewis acid
This is called the Hosoni-Sakurai Reaction (see J. Org. Chem. 2006 71 8516)
Can only find an image for the more common addition to carbonyl compounds ...
- 21.6k
7
votes
Accepted
Why are the products of Grignard reaction on an alpha-chiral ketone diastereomers rather than a racemate?
The reaction introduces a new chiral center into your mix, that chiral carbon being the one that has the tertiary alcohol on it (let’s call this #2).
The product will produce a mixture of those chiral ...
6
votes
Accepted
Why is a Grignard reagent not protonated by chloramine?
The $\ce{N-H}$ protons are relatively weakly acidic and this makes deprotonation kinetically less favored if an alternative nucleophilic attack mechanism is available. With $\ce{NH3}$ no such ...
- 53.2k
6
votes
Accepted
Phenol preparation from Grignard reagent
As requested by the OP - the route that lab chemists use to form phenols from aryl halides (not aryl fluorides) is via formation of the aryl boronic acid or boronate. These may be formed by either ...
- 21.6k
6
votes
Accepted
Grignard alkene on a carbonyl
Nucleophilic acetyl substitution is common among carboxylic acid, acid chlorides, anhydrides, esters, and amides.
Two very common examples are anhydride decomposition and esterification of carboxylic ...
- 39.5k
6
votes
Accepted
Addition of Methyl Grignard and use of HClO4 in this question
Consider the resonance structures of the pyranone. MeMgCl attacks the structure shown second. The perchloric acid workup hydrolyses the enol ether to give the diketone shown bottom right. NaOH ...
- 21.6k
6
votes
Accepted
Will a Grignard reagent react with an epoxide or episulfide first?
There are quite a few reasons why the episulfide might open before the epoxide:
Sulphur is less electronegative than oxygen. Therefore, by Bent's rule , more atomic s-character will be directed by ...
- 3,176
6
votes
Accepted
Priority order of attack of grignard reagents on functional groups
For the compound given in the question, the priority order of Grignard reagent attack follows,
$\ce{R-OH > R-CO-R' > R-COOR'}$
Reason:
Acid-base neutralisation are very fast.
Carbonyl carbon ...
- 3,033
6
votes
Accepted
Grignard reaction with cycloheptatriene
The product A, shown below, is formed by first reducing the ketone to a secondary alcohol with $\ce{LiAlH_4}$ and then by adding a methyl group to form an ether using the reagent $\ce{CH_3I}$.
$\...
- 605
6
votes
Accepted
Can primary amine be produced using Grignard reagent?
Yes indeed. Primary amines can be made using Grignard reagent. The first reported instances of such reaction was found during the 1930s where they used mono/dihaloamines and reacted with Grignard ...
- 25.2k
5
votes
Accepted
Grignard Reagent in THF vs in Diethyl ether
THF has a number of differences with diethyl ether:
Oxygen non-bonding doublets are more available for bonding with magnesium because the 2 ethyl groups are not freely rotating around (you may think ...
- 3,002
5
votes
Compatibility of Grignard reagents with aromatic nitro groups
Aromatic nitro groups are not compatible with Grignards as they react with the nitro group. An example of this being useful is the Bartoli synthesis of indoles from vinyl Grignards (Tet. Letts. 1989, ...
- 21.6k
5
votes
Accepted
Carbonation of Grignard reagent with a carbonyl group present in it
You should look at two things:
1) Will the reaction stay on course? If you add water to the Grignard reagent first, without the carbon dioxide initially, what do you get? Is it something that will ...
- 53.2k
Only top scored, non community-wiki answers of a minimum length are eligible