Write a complete mechanism. Explain each step. Explain the stereo chemical changes. Compare the HNMR peaks of the substrate and the organic product Indicate missing peaks and newly formed peaks in the product.
CH3CH2CH2CH3 + Cl2/light--- CH3CHCLCH2CH3 =HCL
The given reaction involves the reaction between the compound CH3CH2CH2CH3 (butane) and Cl2 (chlorine) in the presence of light to produce the organic product CH3CHClCH2CH3 (2-chlorobutane) and HCl (hydrochloric acid). Let's break down the mechanism and explain each step:
Step 1: Initiation
The reaction is initiated by light, which provides the energy needed to break the Cl-Cl bond in Cl2. This results in the formation of two chlorine radicals (Cl•).
Cl2 + hv (light) -> 2 Cl•
Step 2: Propagation
In this step, one of the chlorine radicals attacks the butane molecule (CH3CH2CH2CH3), resulting in the formation of a butyl radical (•CH2CH2CH2CH3) and HCl.
Cl• + CH3CH2CH2CH3 -> •CH2CH2CH2CH3 + HCl
Step 3: Further Propagation
The butyl radical (•CH2CH2CH2CH3) formed in the previous step reacts with another chlorine molecule, resulting in the substitution of a hydrogen atom on the butyl radical with a chlorine atom. This generates 2-chlorobutane (CH3CHClCH2CH3) and a chlorine radical, which can undergo further reactions.
•CH2CH2CH2CH3 + Cl2 -> CH3CHClCH2CH3 + Cl•
Step 4: Termination
In the termination step, two radicals react with each other to form a stable compound, effectively ending the chain reactions. This can happen between any combination of the chlorine radicals (Cl•) or the butyl radicals (•CH2CH2CH2CH3).
Cl• + Cl• -> Cl2
•CH2CH2CH2CH3 + •CH2CH2CH2CH3 -> butane
Stereochemical Changes:
In terms of stereochemistry, the reaction described does not introduce any new stereochemical centers or cause changes in the existing stereochemistry. The conservation of stereochemistry in this reaction is due to the symmetrical nature of the butane molecule.
HNMR Peaks Comparison:
To compare the HNMR peaks of the substrate (butane) and the organic product (2-chlorobutane), we should consider the impact of the introduction of the chlorine atom on the NMR spectrum.
Substrate (CH3CH2CH2CH3 - butane):
In the substrate, butane, we have 4 different types of hydrogen atoms (CH3, CH2, CH2, and CH3). Each type will contribute a distinct peak in the HNMR spectrum, reflecting its unique chemical environment.
Organic Product (CH3CHClCH2CH3 - 2-chlorobutane):
With the introduction of the chlorine atom, the organic product, 2-chlorobutane, will have new peaks and missing peaks compared to the substrate.
Missing Peaks:
The chlorine atom is not expected to show up in the HNMR spectrum, as it is electronegative and does not have directly attached hydrogen atoms. Therefore, there will be a missing peak corresponding to the chlorine atom in the HNMR spectrum of the organic product.
Newly Formed Peaks:
A new peak will appear in the HNMR spectrum of 2-chlorobutane corresponding to the proton attached to the chlorine atom. This peak will generally appear as a singlet, indicating that the proton is not coupled to any nearby protons.
Overall, while the substrate (butane) would have 4 distinct HNMR peaks, the organic product (2-chlorobutane) would have 3 distinct HNMR peaks (one peak corresponding to the proton attached to the chlorine atom and two peaks corresponding to the remaining protons in 2-chlorobutane).