"1. (a) Write structural formulas for at least 14"
1. (a) Write structural formulas for at least 14 stable compounds that have the formula C4H8O. (b) The IR spectrum of the unknown compound shows a strong peak near 1730 cm-1. Which structures now remain as possible formulas for the compound? (c) The mass spectrum shows the peaks at m/z 44 (the base peak) and m/z 29. Propose a structure for the compound and write fragmentation equations showing how these peaks arise. (a) ethers O O O O O O O O O O O O alcohols OH HO OH OH OH OH OH OH OH Aldehydes and ketones O O O H H (b) O O O H H (c) O H O Ionization O Fragmention O H H + CH 29 O Ionization H Rearrangement OH O + H H H 44 2. Explain the following observations (a) The molecular ion peak of a primary and secondary alcohol is very small; with a tertiary alcohol it is usually undetectable. (b) Primary alcohols show a prominent peak at m/z 31 (c) Secondary alcohols usually give prominent peaks at m/z 45, 59, 73 and so on. (d) Tertiary alcohols have prominent peak at m/z 59, 73, 87 and so on. (a) In mass spectroscopy, the loss of H2O is very common for alcohols. H H H + H2O H R O R O R Tertiary alcohol has more β hydrogens. Therefore it is more likely to lose water. (b) H H H O R O R O R + 31 (c) R R H H H O R O R O R + R 45 when R = methyl 59 when R = ethyl 73 when R = propyl (c) R'' R R'' R +O H H H R' O R' O R' R R'' 59 when R, R'' = methyl 73 when R and R'' are a combination ethyl and methyl 3. Two isomers having molecular formula C4H6O are both symmetrical in structure. In their IR spectra, neither isomer when in dilute solution in CCl4 has absorption in the 3600 cm-1 region. Isomer A has absorption bands at approximately 3080, 1620 and 700 cm-1. Isomer B has bands in the 2900 cm-1 region and at 1780 cm-1. Propose a structure for A and possible structures for B. O O A B 4. Write structural formulas for each of the following: (a) Three primary alcohols with the formula C4H8O. (b) A secondary alcohol with the formula C3H6O. (c) A tertiary alcohol with the formula C4H8O. (d) Three ketones with the formula C5H10O. (e) A tertiary amine with formula C3H7N. (a) OH HO OH OH OH (b) OH (c) OH (d) O O O (e) N 5. Propose a structure for the compound that has a molecular formula C11H14O2. It has a tert-butyl group in the structure. Also show the dimer via hydrogen bonding (Show the hydrogen bonding between 2 molecules.) O OH H O O t-Bu t-Bu O O H t-Bu Extra problem 1 (a) Br (b) 4 Br (c) or (d) Br79 2 EDACB