In acidic aqueous solution, the complex trans -[Co(en) 2 Cl 1 ] 2+ (aq) undergoes the following substitution reaction: trans -[Co(en) 1 Cl 2 ] + (aq) + H 2 O(l) → trans -[Co(en) 2 (H 2 O)Cl] 2+ (aq) + Cl – (aq) The reaction is first order in trans -[Co(en) 2 Cl 2 ] + (aq), and the rate constant at 25°C is 3.2×10 –5 s –1 . (d) Is the reaction product chiral or achiral? Explain.

All right. Hi, everyone. So for this question, let's consider the acid hydrolysis reaction of the complex ion cis Coen two N CS cl positive. The reaction is a pseudo first order reaction with a rate constant of 1.1 multiplied by 10 to the power of negative five inverse seconds at 25 °C determine whether the product is Cairo or a Cairo and justify your answer. And here we have four different answer choices proposing whether or not the product is Cairo or a Cairo depending on whether or not its sis structures are identical or not. So first, let's start by writing out the name of the product form. It is sis co en two N CS h2o close brackets to positive. So here based on this information, the central metal ion is going to be Cobalt to positive. And in this case, we happen to have a few different Liggins. The first of which is me actually move this, the first of which is en which is the abbreviation of Celine Diamine. And recall that Ethylene diamine is a B dentate ligand that has two donor atoms capable of connecting to the central metal ion in two different locations. In this case, our nitrogen atoms are the the donor atoms. On the other hand, our next legend is N CS minus which is or iso tho cyano ligand, which happens to be mono dentate. Therefore, only having one donor atom. Next is water referred to as aqua as a ligand, which is also monogenic. Now recall that bent ligands contribute a co-ordination number of two or as mono dentate ligands contribute a co-ordination number of one. So considering the fact that I have two B dentate ligands in this molecule and two mono dentate leggings, that means that my co ordination number is equal to six, which means that the geometry of this compound is going to be octahedral. Now recall also that the prefix sis indicates that two ligands are located to adjacent corners of the octahedron, right. So let's start by drawing the structure here is Cobalt in the center and I will start off by drawing by ethylene diamine ligands. So the curve that's combining my two nitrogens together represents the two carbons in between both nitrogens and ethylene diamine. And now I will be adding my molecule of water as well as N CS. So the first step is to imagine a mirror image of the compound I just drew. So I will withdraw my Cobalt center and then I'm going to add the same leggings. However, on the opposite sides to reflect that they are supposed to be mirror images of each other. So here are the mirror images of each other. So now that we've generated the mirror images of our product, the question is whether or not these mirror images are super imposable to each other. So to visualize this better, I'm going to actually rotate the first structure. So that now my ethylene diamine are on the left side. And also I'm going to go ahead and rotate the first structure horizontally should be N CS, right. So now when I compared these structures together, after rotating, the first one, I recognize that they are actually non super imposable mirror images of each other, they are non superimposable, which means that they are not the same molecule. Therefore, our product here is actually a Cairo complex. So our answer is going to be option B in the multiple choice, right. The product is a chiral molecule because it has non identical cyst structures. And with that being said, thank you so very much for watching. And I hope you found this helpful.

Ch.21 - Transition Elements and Coordination Chemistry

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McMurry 8th Edition

Ch.21 - Transition Elements and Coordination Chemistry

Problem 21.138d

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Chapter 21, Problem 21.138d

In acidic aqueous solution, the complex trans-[Co(en)₂Cl₁]²⁺(aq) undergoes the following substitution reaction:
trans-[Co(en)₁Cl₂]⁺(aq) + H₂O(l) → trans-[Co(en)₂(H₂O)Cl]²⁺(aq) + Cl^–(aq)
The reaction is first order in trans-[Co(en)₂Cl₂]⁺(aq), and the rate constant at 25°C is 3.2×10^–5 s^–1.
(d) Is the reaction product chiral or achiral? Explain.

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Identify the structure of the product, trans-[Co(en)2(H2O)Cl]2+. Here, 'en' stands for ethylenediamine, a bidentate ligand, which means it can form two bonds with the cobalt ion. The product also contains a water molecule and a chloride ion as ligands.

Analyze the geometry of the complex. The cobalt ion in the complex is likely to adopt an octahedral coordination geometry because it is bonded to six sites, which are occupied by the two bidentate ethylenediamine ligands, one water molecule, and one chloride ion.

Consider the arrangement of the ligands around the cobalt ion. In a trans configuration, two identical ligands are opposite each other. In this complex, the two ethylenediamine ligands are likely opposite each other, with the water and chloride ion also opposite each other.

Determine the symmetry of the complex. For a complex to be chiral, it must lack any internal planes of symmetry. The presence of a mirror plane would make the complex achiral.

Conclude whether the complex is chiral or achiral based on the symmetry. Since the complex has a trans arrangement with likely mirror planes between the opposite ligands, it is typically considered achiral.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, leading to two distinct enantiomers. In contrast, achiral molecules can be superimposed on their mirror images and often possess a plane of symmetry.

Coordination Complexes

Coordination complexes consist of a central metal atom or ion bonded to surrounding molecules or ions called ligands. The arrangement and type of ligands can significantly influence the properties of the complex, including its chirality. In the case of the given reaction, the coordination environment around the cobalt ion changes, which can affect whether the resulting complex is chiral or achiral.

Substitution Reactions in Coordination Chemistry

Substitution reactions in coordination chemistry involve the replacement of one ligand in a complex with another. These reactions can lead to changes in the geometry and electronic properties of the complex. The specific nature of the ligands and their arrangement can determine the chirality of the product, as seen in the transformation of the cobalt complex in the question.

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Textbook Question

In acidic aqueous solution, the complex trans-[Co(en)₂Cl₁]²⁺(aq) undergoes the following substitution reaction:

trans-[Co(en)₂Cl₁]⁺(aq) + H₂O(l) → trans-[Co(en)₂(H₂O)Cl]²⁺(aq) + Cl^–(aq)

The reaction is first order in trans-[Co(en)₂Cl₂]⁺(aq), and the rate constant at 25°C is 3.2×10^–5 s^–1.

e. Draw a crystal field energy-level diagram for trans-[Co(en)₂Cl₂]⁺ that takes account of the fact that Cl^– is a weaker-field ligand than ethylenediamine.

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Cobalt(III) trifluoroacetylacetonate, Co(tfac)₃, is a sixc oordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:

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Cobalt(III) trifluoroacetylacetonate, Co(tfac)₃, is a sixcoordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:

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