Concept explainers
Following are 1H-NMR spectra for compounds G, H, and I, each with the molecular formula C5H12O. Each is a liquid at room temperature, is slightly soluble in water, and reacts with sodium metal with the evolution of a gas.
(a) Propose structural formulas of compounds G, H, and I.
(b) Explain why there are four lines between δ 0.86 and 0.90 for compound G.
(c) Explain why the 2H multiplets at δ 1.5 and 3.5 for compound H are so complex.
(a)
Interpretation:
Following compounds G,H and I stractural formula has to be proposed with the help of given molecular formula
Concept introduction:
The
Chemical shift: The NMR spectrum of any compound is taken with reference to a standard compound called reference compound. Generally, tetramethylsilane (TMS) is taken as the reference compound. The methyl protons of TMS are equivalent and produces only one sharp peak at the rightmost end of the scale.
The distance between the TMS signal and the signals produced by the compound is called the chemical shift. Chemical shift basically measures the shift in the signal position of the compound with respect to the reference signal.
Chemical shift in delta scale is given as,
Explanation of Solution
Index of Hydrogen Deficiency (IHD) calculation,
Given molecular formula is
We calculate the
From the molecular formula, there is an index of hydrogen deficiency is zero for these molecules, so there are no rings (or) double bonds.
The fact that the compounds are slightly soluble in water and react with sodium metal indicates that each molecule has an hydroxyl
The
There are 5 peaks observed in the given
A multiplet is observed for 1 hydrogen at around
The one doublet is observed for 1 hydrogen at around
Another one multiplet is observed for one hydrogen at around
One doublet is observed for 3 hydrogens at around
The one doublet is observed for 6 hydrogens at around
Based on the above
The
There are 5 peaks observed in the given
The
There are 5 peaks observed in the given
Based on the above
(b)
Interpretation:
The following compound-G has four lines observed in the range of
Concept introduction:
The
Diastereotopic: If the protons are not interchangeable by either of the symmetry operations, then the protons are Diastereotopic; the protons are not chemically equivalent if a chiral center present in the molecule.
Explanation of Solution
Let us consider the given compound-G:
Above the molecule, the carbon atom 2 attached with hydroxyl
That is makes the two methyl groups are diastereotopic, so they have different chemical shifts, the four lines are actually two doublets.
(c)
Interpretation:
The Following compound-H is two hydrogens appread at multiplet, this compound is complex or not, the behaind reason should be explained.
Concept introduction:
The
Chemical shift: The NMR spectrum of any compound is taken with reference to a standard compound called reference compound. Generally, tetramethylsilane (TMS) is taken as the reference compound. The methyl protons of TMS are equivalent and produces only one sharp peak at the rightmost end of the scale.
The distance between the TMS signal and the signals produced by the compound is called the chemical shift. Chemical shift basically measures the shift in the signal position of the compound with respect to the reference signal.
Chemical shift in delta scale is given as,
Diastereotopic: If the protons are not interchangeable by either of the symmetry operations, then the protons are Diastereotopic; the protons are not chemically equivalent if a chiral center present in the molecule.
Explanation of Solution
Let us consider the given compound-H:
Above the molecule, the carbon atom 2 attached with hydroxyl
This chiral center makes the adjacent
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