The base peak in the mass spectrum of 2,2,5,5-tetramethylhexane (molecular mass = 142) is at m/z = 57, which corresponds to a composition of C4H9. Suggest a structure for the fragment that accounts for this peak and offer a reason for why this fragment is so abundant.

The volatile organic compounds (VOCs) produced by decomposing tissue and organs were studied in an effort to identify possib human-specific markers (PLoS ONE 2015 10(9): e0137341.). Of 452 VOCs isolated, six were found to be unique to humans, so th prove to be a useful tool for forensic chemists trying to determine the source of unidentified remains. There are two doublets in expected ¹H NMR spectrum of the following human-specific VOC. Identify the protons giving rise to each doublet. 1 2 H3C H3C- оооооооо 238 H 8 HH HH 3 HH CH3 5 7 Identify the two groups of protons that give rise to the doublets in the spectrum. CH3 8

2. How could you use the 4 (FOUR) forms of spectroscopy that we have discussed to give you an indication that you have 100% conversion of alcohol (cyclohexanol) to alkene (cyclohexene), i.e.-the reaction went to completion? Use ALL relevant specific signals that you could monitor to support your answer. If a technique would not help you at all, indicate the reason for this. (a) IR spectroscopy (b) Mass spectroscopy (c) BC NMR Spectroscopy (d) 'H NMR Spectroscopy

The mass spectrum of 3-ethyl-3-methylheptane [(CH3CH2)2C(CH3)CH2CH2CH2CH3] shows fragments at m/z = 127, 113, and 85. Propose structures for the ions that give rise to these peaks