(a) From the elemental analysis the empirical formula of Compound Q is C₅H₁₂O.

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(b) The M⁺ peak at m/z = 88 is evidence that the molar mass is 88 g mol^-1 and hence the molecular formula of Compound Q is the same as its empirical formula, C₅H₁₂O. The fragment at m/z = 73 is due to loss of an methyl group, –CH₃ leaving C₄H₉O⁺. The fragment at m/z = 45 is due loss of –C₃H₇ leaving C₂H₅O⁺ with the peak at m/z = 43 due to C₃H₇⁺.   

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(c) From its molecular formula Compound Q could either be an alcohol or an ether. The broad absorption at about 3300 cm^-1 is indicative of the presence of an –OH bond and hence Compound Q is an alcohol. The peaks at approximately 3000 cm^-1 are due to C–H absorptions. The absorption at 1050 cm^-1 is likely to be due to the presence of a C−O single bond.

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(d) The ¹H NMR spectrum shows that the twelve hydrogen atoms are in five different chemical environments in the ratio 6:3:1:1:1. The doublet at 0.9  ppm suggests two methyl groups attached to a carbon atom containing one H atom. Similarly the doublet at 1.1 ppm suggests one methyl group attached to a carbon atom containing one H atom. The two protons with complex splitting patterns with integration traces of one indicate two separate C−H entities bonded to adjacent carbon atoms that contain more than three protons.  The one at 3.6 ppm is due to the C−H proton adjacent to the carbon atom containing the −OH group. The remaining singlet at 1.8 ppm is due to the hydrogen atom of the –OH group as this will not be split.
 

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All this information taken together confirms that Compound Q is 3-methylbutan-2-ol, CH₃CH(OH)CH(CH₃)₂.

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