Question

What is the formula and structure of the compound given the IR and NMR data?

6.0 0.30 0.912 anะ 2. 59 6 - . 86 - 35 ปี - 5,254 1. 332 - - 15 0.336 5.0 - 5.173 5. 057 - 5,031 4.5 0.307 4,315 -4.239 4. 284 4,268 8วา “H C: 04 (43 3.0 25 ว15 2.0 C. 47. -1.91 1.00 1.250 PPTT

Answer 1

Name: but-3-en-2-ol Chemical Formula: C4H80 Molecular Weight: 72.11 Proposed Structure е OH d Degree of Unsaturation=C+ 1_N 2 2 2 =5+1-4.5-0.5 = 1 FTIR: Wave number (cm) 3450 3100 2980 1500 1470 bond -OH stretching C-H stretching C-H stretching C=C stretching C-H bend Functional group. alcohol alkene alkane alkene alkane 1H NMR #Hydrogen 3 1 1H Signal H marked a H marked b H marked c H marked d H markede Chemical Shift (ppm) 1.2 4.3 5.9 5.0 and 5.2 1.9 Multiplicity doublet multiplet multiplet Two doublets singlet 1 and 1

Mass Fraction: The molecular weight of the compound is 72 g/mol so the molecular ion peak is appearing at 72. Multiplicity Rule: The multiplicity of any peak depends on the number of neighboring protons. If a protons contain n number of neighboring protons then the splitting will be n+1. Suppose a proton contains 2 neighboring H then it will give a triplet (2+1). However sometimes the splitting changes due to germinal vicinal etc. coupling in certain cases. The DoU of the compound is 1. It has a pi-bond. The presence of the terminal double bond is confirmed by the characteristics peak for the terminal allyl i.e multiplet at 5.9 ppm for 1H and two doublets at 5.0 and 5.2 ppm. The two protons in the terminal alkene CH2 couples differently with the adjacent proton (cis/trans) because of the restricted free rotation due to the double bond. Hence two different doublets appear for the CH2 and one multiplet for the CH. The presence of -OH is confirmed by the FTIR peak at 3450 cm-1. The terminal CH3 appears at 1.2 ppm and the CH attached to the alcohol appears at 4.3 ppm.