The acid-catalyzed hydration of symmetrical alkynes produces one ketone: Unsymmetrical alkynes show no preference as to what carbon gets the OH and as a result, a mixture of two ketones is obtained: Terminal alkynes also undergo acid-catalyzed hydration.
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Oct 26, 2015 · 9 . Which one of the following alkynes gives a single ketone in the acid - catalyzed hydration of each ?
• However, alkynes undergo mercury (II) catalyzed hydration. • Mercuric (II) sulfate is a Lewis acid catalyst that promotes addition of water to alkynes in Markovnikov orientation. • As in hydroboration, the immediate product is a vinylic alcohol , or enol , which spontaneously tautomerises to a ketone.
Chemistry questions and answers. 38. In an acid-catalyzed hydration, which of the following alkynes is expected to produce a single ketone? A 2-decyne B. 3-decyne C. 4-decyne D. 5-decyne E. All of the above will give a single product. Question: 38.
Chemistry questions and answers. Which one of the following alkynes gives a single ketone in the acid-catalyzed hydration of each? 3-decyne a b. 2-decyne c. 4-octyne 4-decyne d.
answer choices. Methanol is more acidic than the alkyne and will be deprotonated instead. Sodium amide is not a strong enough base to deprotonate the alkyne. Sodium amide in methanol reduces alkynes to alkenes. Methanol is toxic, and should be avoided when possible.
Only sodium amide is a strong enough base to deprotonate a carbon. The above statement is false; terminal alkynes are not produced under the given conditions. Terminal alkynes are more stable than the internal alkynes, and are always the favored product.
Q. Select the best explanation for why methanol, CH 3 OH, cannot be used as a solvent for the deprotonation of a terminal alkyne by sodium amide, NaNH 2. answer choices. Methanol is more acidic than the alkyne and will be deprotonated instead. Sodium amide is not a strong enough base to deprotonate the alkyne.
The acid-catalyzed hydration of symmetrical alkynes produces one ketone:
Draw the major product (s) expected when each of the following alkynes is treated with aqueous acid in the presence of mercuric sulfate (HgSO4):
Draw the major product (s) expected when each of the following alkynes is treated with aqueous acid in the presence of mercuric sulfate (HgSO4):
With the addition of water, alkynes can be hydrated to form enols that spontaneously tautomerize to ketones. Reaction is catalyzed by mercury ions. Follows Markovnikov’s Rule: Terminal alkynes give methyl ketones.
Once the hydrogen is bound you have a carbocation, which gets attacked by the water molecule. Now you have a positive charge on the oxygen which results in a base coming in and deprotinating the molecule. Once deprotinated, you have an enol, which then gets tautomerized.
Study Notes. Rapid interconversion between tautomers is called tautomerism; however, as the two tautomers are in equilibrium, the term tautomeric equilibrium may be used. This section demonstrates the equilibrium between a ketone and an enol; hence, the term keto – enol tautomeric equilibrium is appropriate.
Tautomeric equilibria are catalyzed by traces of acids or bases that are generally present in most chemical samples. The three examples shown below illustrate these reactions for different substitutions of the triple-bond. The tautomerization step is indicated by a red arrow.
Acid-Catalyzed hydration is the addition of water to an alkene which forms an alcohol: The reaction goes through a stepwise mechanism which starts with the protonation of the double bond: The presence of an acid is necessary as the water by itself is a weak acid and cannot protonate the double bond. However, the hydronium ion, formed in acid ...
The presence of an acid is necessary as the water by itself is a weak acid and cannot protonate the double bond. However, the hydronium ion, formed in acid solutions, is strong enough and the electron-rich double bond attacks it to form a carbocation. Once the carbocation is formed, it can now be attacked by the water: ...