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Question: Allylides are ionic carbides. They contain: A. \({C^{4 - }}\) ions B. \({C_2}^{2 - }\) ions C....

Allylides are ionic carbides. They contain:
A. C4−{C^{4 - }} ions
B. C22−{C_2}^{2 - } ions
C. C33−{C_3}^{3 - } ions
D. C34−{C_3}^{4 - } ions

Explanation

Solution

For solving this type of question, first we need to understand the basic concepts of allylides. As we know that, allylides are ionic carbides. So, we need to understand what carbide is. Carbide is a compound which is composed of carbon and a metal. Metallurgically, the process of carbiding or carburizing is used for producing carbide coatings on a metal piece.

Complete step by step answer:
We must know that the ionic carbides are substances which have discrete C- anions that are present in the form C4−{C^{4 - }} ions which are known as methanides. These methanides are known to be derived from methane written as CH4C{H_4} having C22−{C_2}^{2 - } ions known as acetylides which are derived from acetylene C2H2{C_2}{H_2} and C34−{C_3}^{4 - } ions which are derived from allene i.e., C3H4.{C_3}{H_4}.
When we perform hydrolysis with water then allylides gives 1-propyne as the resultant of the reaction. Let’s refer to the chemical reaction of the hydrolysis with water:
Mg2C3+4H2O→2Mg(OH)2+CH3−C≡CHM{g_2}{C_3} + 4{H_2}O \to 2Mg{(OH)_2} + C{H_3} - C \equiv CH
By referring to this reaction, we need to focus that the allylides contain such type of compounds:
C34−→[C−C≡C]4−{C_3}^{4 - } \to {[C - C \equiv C]^{4 - }}
∴\therefore Option D is the correct answer.
Hence, we need to understand that the alkaline earth metal cation of an allylide get dissolved in dry ether in the presence of an alkyl halide to form Grignard’s reagent.

Note:
We also need to know about interstitial carbides which are derived from relatively large transition metals that act as a host lattice for the small carbon atoms. These Carbon atoms occupy the interstices of the close-packed metal atoms. They are characterized by extreme hardness and at the same time there is extreme brittleness. These carbides have very high melting points ranging from 3,000 to 4,000 °C and retain many of the properties associated with the metal, like high conductivity of heat and electricity as well as metallic luster.