FH2O2Resonance [α]λ SN1E1 ME2SOCl2 TS Enan R. Chem 250-02 Fall, 2014 T BH3 A syN KOtBu SN2 FH2O2Resonance [α]λ mG (R) E1cb C-HAIR Trans SN1E1 ME2SOCl2 TS Enan R.

CHEM 250-02 Class 39 Thanks for a Really Great Semester Review Sessions Prof. Keyser – Bring a Question Tuesday 12/9/14 10:00 - 12:00 BC-218 Wednesday 12/10/14 10:00 - 12:00 BC-218 FINAL EXAM: Friday 12/12/14 8:30 am - 11:30 am HS-139 Bring your model kits, pencils, (calculator) Send in questions to Dr. R.

Carbon !

High Resolution MS Masses can be measured to 1 part in 20,000 ! Masses can be measured to 1 part in 20,000 ! A molecule with nominal mass of 44 could be C3H8, C2H4O, CO2, or CN2H4. If a more exact mass is, for example 44.029, pick the correct structure from: C3H8 C2H4O CO2 CN2H4 44.06260 44.02620 43.98983 44.03740

Mass Spectra 1-Bromopropane CH3-CH=CH2 + HBr in air  MS of Propane CH3-CH2-CH3

1-bromopropane  propene  2-bromopropane 1-bromopropane  propane  2-bromopropane 43 CH3CH2CH2-Br (CH3)2CH+

Mass Spectrometry The presence of Bromine in a compound The two (2) principal Bromine Isotopes in nature are Br-79 and Br-81 (2 additional Neutrons in Br-81) The relative abundance ratio of 79Br to 81Br is 100 : 97.1 or 50.5 : 49.5 or  1 : 1 Molecules containing a single Bromine atom will also show two molecular ion peaks one for Br-79 (M+) and one for Br-81 M+2). Based on the natural abundance ratio of 100 / 97.1 (about 1:1), the relative intensity of the 79Br peak will be about the same as the 81Br peak. Note: Fluorine exists in nature principally as a single isotope - 19F9 Therefore, you will see a single Molecular Ion peak (assuming no other Halogens present).

bromotoluene  Methylbenzene  benzylbromide

Mass Spectra 1- and 2-Chloropropane 43 MS of CH3CH2CH2-Cl

Mass Spectrometry The Presence of Chlorine in a Compound The two (2) principal Chlorine Isotopes in nature are Cl-35 and Cl-37 (2 additional Neutrons in Cl-37) The relative abundance ratio of 35Cl to 37Cl is 100 : 32.6 or 75.8 : 24.2 or  3 : 1 Therefore, a Molecule containing a single Chlorine atom will show two Mass Spectrum Molecular Ion peaks, one for Cl-35 (M+) and one for Cl-37 (M+2) Note: M+2 denotes 2 more neutrons than M+ Based on the natural abundance ratio of 100 / 32.6 (about 3:1), the relative intensity (peak height) of the Cl-35 peak will be 3 times the intensity of the Cl-37 peak.

Mass Spectra C5H12 pentane 2-methylbutane 2,2-dimethylpropane

EI MS – Alkanes n-Hexane (C6H14) 57 41, 43 27, 29 71

EI MS 2,2-dimethylpropane is the parent ion detected ?

Chem Act 16, page 253

Chem Act 16, page 254

Chem Act 16, page 256

Chem Act 16, page 259

A New Carbon C60 eI MS

13C 1H Carboxylic acids ~ 10-13 ppm Aldehydes RCHO ~ 10 ppm

Chem Act L-4 Exercise 12. (page 308) [M]+ = 136 (100) [M+1]+ = 137 (3.3) [M+2]+ = 138 (97.3) 1H NMR: 1.9 (d, 3H) 4.5 (at least 5 lines, apparent pentuplet (?), 1H) 9.7 (d, 1H)

Problem 13. 54: Propose a structure and assign peaks Problem 13.54: Propose a structure and assign peaks. Formula = C4H7O2Cl IR absorption peak at 1740 cm-1 MS m/z 122 (relative intensity 3), 124 (relative intensity 1)

Propose a structure consistent with all of the following data. t, 3H q, 2H

Problem 13.45b C4H8Cl2

Problem 13.58a C5H10O

ChemAct L3 Exercise 13 & 14