$CH _{3} C \equiv CCH _{3} \xrightarrow{H 2 / P t} A \xrightarrow{D_{2} / P t} B$ The compounds $A$ and $B$, respectively are
- cis-butene-2 and rac-2, 3-dideuterobutane
- trans-butene-2 and rac-2, 3-dideuterobutane
- cis-butene-2 and meso-2, 3-dideuterobutane
- trans-butene-2 and meso-2, 3-dideuterobutane
The Correct Option is C
Solution and Explanation
. Alkynes are catalytically hydrogenated to produce cis-alkene, which is then further hydrogenated in the presence of platinum to produce meso-2,3-dideuterobutane. The conversion of is the net response of C≡C to C-C with the addition of two molecules of H2 and D2
Alkynes may be hydrogenated by simply adding hydrogen atoms across their triple bonds. Alkane results from the formation of a carbon-carbon double bond, while alkene results from the formation of a carbon-carbon single bond.
A bond will be lost if hydrogen atoms are added across a double bond.
The result of hydrogenating the provided alkyne is
Furthermore, the double bond in cis-2-butene is broken down into a single bond and an alkane is produced when deuterium is added in the presence of a platinum catalyst.
Meso compounds are substances that contain a centre of symmetry and are optically active, meaning they exhibit a non-superimposable mirror image.
A racemic mixture is a collection of substances with both a (R) and a (S) structure.
The compound produced cannot be a racemic combination because it displays optical activity.
The resultant product is a meso compound in this case because it possesses a plane of symmetry and a non-superimposable mirror image that makes it optically active
So, the correct answer is cis-butene-2 and meso-2,3-dideuterobutane.
Top Questions on Alkynes
The product of hydrolysis of propyne in the presence of 1% \( HgSO_4 \) and 40% \( H_2SO_4 \) is ___________.
- The incorrect statement regarding ethyne is
The structures of major products A , B and C in the following reaction are sequence
- General formula of alkynes
- Given below are two statements:
Statement-I : In Hofmann degradation reaction, the migration of only an alkyl group takes place from carbonyl carbon of the amide to the nitrogen atom.
Statement-II : The group is migrated in Hofmann degradation reaction to electron deficient atom.
In the light of the above statements, choose the most appropriate answer from the options given below:
Questions Asked in BITSAT exam
- Let \( ABC \) be a triangle and \( \vec{a}, \vec{b}, \vec{c} \) be the position vectors of \( A, B, C \) respectively. Let \( D \) divide \( BC \) in the ratio \( 3:1 \) internally and \( E \) divide \( AD \) in the ratio \( 4:1 \) internally. Let \( BE \) meet \( AC \) in \( F \). If \( E \) divides \( BF \) in the ratio \( 3:2 \) internally then the position vector of \( F \) is:
- BITSAT - 2024
- Vectors
- Let \( \mathbf{a} = \hat{i} - \hat{k}, \mathbf{b} = x\hat{i} + \hat{j} + (1 - x)\hat{k}, \mathbf{c} = y\hat{i} + x\hat{j} + (1 + x - y)\hat{k} \). Then, \( [\mathbf{a} \, \mathbf{b} \, \mathbf{c}] \) depends on:}
- BITSAT - 2024
- Vectors
- Let the foot of perpendicular from a point \( P(1,2,-1) \) to the straight line \( L : \frac{x}{1} = \frac{y}{0} = \frac{z}{-1} \) be \( N \). Let a line be drawn from \( P \) parallel to the plane \( x + y + 2z = 0 \) which meets \( L \) at point \( Q \). If \( \alpha \) is the acute angle between the lines \( PN \) and \( PQ \), then \( \cos \alpha \) is equal to:
- The magnitude of projection of the line joining \( (3,4,5) \) and \( (4,6,3) \) on the line joining \( (-1,2,4) \) and \( (1,0,5) \) is:
- BITSAT - 2024
- Vectors
- The angle between the lines whose direction cosines are given by the equations \( 3l + m + 5n = 0 \) and \( 6m - 2n + 5l = 0 \) is:
- BITSAT - 2024
- Vectors
Concepts Used:
Alkynes
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon-carbon triple bond. Alkynes are an organic molecule that contains triple bonds between the carbon atoms. Its general formula is CnH2n-2. They are also known as acetylenes. In this article, we will deal with the structure of alkynes.
Isomerism in Alkynes:
Alkynes show three types of isomerism
- Chain isomerism - Due to the different arrangement of carbon atoms in the chain that is straight chain or branched.
- Position isomerism - Due to the difference in the location of the triple bond.
- Functional isomerism - Isomeric with alkadienes both being represented by the general formula CnH2n-1.
Properties of Alkynes:
Physical Properties:
- Non-polar, unsaturated hydrocarbons.
- Highly soluble in organic and non-polar solvents and slightly soluble in polar solvents.
- High boiling point, in comparison to other hydrocarbons.
- Release a high amount of energy due to the repulsion of electrons in a reaction.
- More acidic than alkanes and alkenes due to SP hybridization.
Chemical Properties:
- Hydrogenation - Alkynes undergoes two types of hydrogenation reactions. Complete hydrogenation (in presence of Pd-C/ H2) and partial hydrogenation (in presence of Linder’s catalyst/H2).
- Act as a strong nucleophile by converting into acetylide.
- React with BH3 and undergo hydroboration reactions to form aldehydes and ketones.
- Undergo halogenation reactions in the presence of different halogenating agents by different mechanisms and forms haloalkanes.