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Question: Choose the correct alkynes which gives alkanal on hydroboration and hydrolysis? A. \(C{H_3} - C \e...

Choose the correct alkynes which gives alkanal on hydroboration and hydrolysis?
A. CH3−C≡C−CH3C{H_3} - C \equiv C - C{H_3}
B. CH3−CH2−CH=CH−C≡CC{H_3} - C{H_2} - CH = CH - C \equiv C
C. CH3−C≡CHC{H_3} - C \equiv CH
D. CH3−CH2−C≡C−CH3C{H_3} - C{H_2} - C \equiv C - C{H_3}

Explanation

Solution

Alkanals or aldehyde, are any of a class of organic compounds, in which a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms.

Step by step solution:
First we must understand what is hydroboration and hydrolysis:
Hydroboration is the process wherein the hydrogen boron bond is added to a double bond between either carbon and carbon or carbon and nitrogen. It can also be performed on a carbon-carbon triple bond.
And in very simple words hydrolysis is a chemical process in which a molecule of water is added to a substance.
In option (A) CH3−C≡C−CH3C{H_3} - C \equiv C - C{H_3}
It is an internal alkyne.
It gives alkanone or ketone CH3−CH2−CO−CH3C{H_3} - C{H_2} - CO - C{H_3} on hydroboration and hydrolysis.
In option (B) CH3−CH2−CH=CH−C≡CC{H_3} - C{H_2} - CH = CH - C \equiv C
It is a terminal alkyne.
But it will give alkenal CH3−CH2−CH=CH−CH2CHOC{H_3} - C{H_2} - CH = CH - C{H_2}CHO on hydroboration and hydrolysis.
In option (D) CH3−CH2−C≡C−CH3C{H_3} - C{H_2} - C \equiv C - C{H_3}
It is also an internal alkyne.
It gives alkanone or ketone CH3−CH2−CO−CH3C{H_3} - C{H_2} - CO - C{H_3} on hydroboration and hydrolysis
In option (C)
Terminal Alkynes CH3−C≡CHC{H_3} - C \equiv CH gives alkanal (CH3−CH2−CHO)\left( {C{H_3} - C{H_2} - CHO} \right)on hydroboration and hydrolysis as:
CH3−C≡CH→hydrolysishydroborationCH3−CH=CHOH→ketoenoltautomerismCH3−CH2−CHOC{H_3} - C \equiv CH\xrightarrow[{hydrolysis}]{{hydroboration}}C{H_3} - CH = CHOH\xrightarrow{{ketoenoltautomerism}}C{H_3} - C{H_2} - CHO

Hence option (C) can be considered as the correct option.

Note:
1. Alkanals are organic molecules containing only carbon (C), hydrogen (H) and oxygen (O) atoms.
2. Alkanals belong to the group of organic compounds known as aldehydes.
3. Aldehydes contain a C=OC = O carbonyl(1), functional group.
4. A straight-chain alkanal consists of a chain of 1 or more carbon atoms joined to each other by single covalent bonds, with a C=OC = O functional group attached to the terminal (end) carbon atom in the chain of carbon atoms.