Chem 51LB Week Summer Session 1 Kevin Chen

Lecture Outline Class website, syllabus and other important information Experiment #1: Infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy Experiment #2: Nucleophilic substitution (Part 1 of 2)

My Goals for 51LB Three main goals – Instill the proper respect for safe lab practices – Teach organic chemistry lab techniques, data analysis, critical thinking skills, etc. – Brainwash students that organic chemistry can be fun! Secondary goals – Catch cheaters… – Survive the heat…

My Goals for 51LB Three main goals – Instill the proper respect for safe lab practices – Teach organic chemistry lab techniques, data analysis, critical thinking skills, etc. – Brainwash students that organic chemistry can be fun! Secondary goals – Catch cheaters… – Survive the heat… while wearing long pants, shirt with sleeves, and close toe shoes

Administrative information Class website: – Syllabus, safety information, lab manual, etc. Office hours: Monday 1:00 – 2:00 PM Tuesday 1:00 – 2:00 PM RH 550

Online tools  Grades  Prelab, dry lab  All sorts of lab reports  Help from peers and TAs (maybe) My  Administrative questions, not for whining

Questions via I cannot sign up for sapling  Use lab section course code. When are sapling due  follow the due dates (first week, you have some buffer) Turnitin.com issues  Make sure you have an account and your TAs will add you to your sections. Where is the syllabus  Working on it… but it will be on the class website. I cannot sign up for ELN  Use the link in my first to the class

Your Awesome TAs 40141: MW 2:00-6:00PM Krista 40142: TuTh 9:00-1:00PM Hurik 40143: TuTh 9:00-1:00PM Krista 40145: TuTh 2:00-6:00PM Michael Ask them for their office hours and s All administrative questions, please ME!

Grades breakdown Daily in-lab scores (~17%): 15pts x 7 labs Lab reports (~26%): 40pts x 3 report scaffolds 45pts x 1 full report Unknowns report (~11%): 70 pts IR/NMR worksheet (~5%): 40 pts Sapling (~7%) Dry lab (~3%) Practical (~30%): 180 pts

Grades breakdown Daily in-lab scores (~17%): 15pts x 7 labs Lab reports (~26%): 40pts x 3 report scaffolds 45pts x 1 full report Unknowns report (~11%): 70 pts IR/NMR worksheet (~5%): 40 pts Sapling (~7%) Dry lab (~3%) Practical (~30%): 180 pts

Sapling reminder! Pre-lab assignments must be COMPLETE 2 hours before your lab time, or no lab for you! Complete means on every question you have either – Found the correct answer – OR – Given up and viewed solution NO EXCEPTIONS!

Grades breakdown Daily in-lab scores (~17%): 15pts x 7 labs Lab reports (~26%): 40pts x 3 report scaffolds 45pts x 1 full report Unknowns report (~11%): 70 pts IR/NMR worksheet (~5%): 40 pts Sapling (~7%) Dry lab (~3%) Practical (~30%): 180 pts

Practical! The single most important factor in determining your grades 2 hour exam – Dry lab  critical thinking question, IR/NMR, mechanism, etc. – Wet lab  organic chemistry lab techniques!

Experiment #1: IR and NMR Given 6 unknowns with different functional groups – Carboxylic acid, ester, ketone, aldehyde, amide, amine, alcohol, aromatic (benzene), etc… – 2 of 6 IR and 6 of 6 NMR spectra will be given Task: perform IR of unknowns (4x) Goal: identify unknowns with IR AND NMR

Infrared Spectroscopy Measures resonant frequency (energy, E = hv) absorbed by organic molecule Resonant frequency = bond vibrational energy Many ways bonds can vibrate Unit: wavenumber (cm -1 ) Different functional group absorbs different frequency!

IR Analysis Shorter bonds = stronger bonds = need more energy = higher frequency (shorter wave) sp (alkyne) > sp2 (alkene) > sp3 (alkane) 1.20Å 1.34Å 1.54Å 3300 cm cm cm -1 Resonance matters (∆ bond length) Consider… alcohol vs ketone vs carboxylic acid

Infrared Spectroscopy

Nuclear Magnetic Resonance H NMR (proton) and C NMR (carbon) Chemical shift, splitting pattern and integration – Different magnetic environment means different chemical shift – Splitting pattern comes from (n+1 rule) and leads to singlet, doublet, triplet, etc – Integration means # of protons

2-pentanone

Identify different types of protons

Simple splitting pattern (n+1 rule) Ha  3H, n = 0  n+1 = 1 (singlet) Hb  2H, n = 2  n+1 = 3 (triplet) Hc  2H, *n = = 5  n+1 = 6 (sextet) Hd  3H, n = 2  n+1 = 3 (triplet)

Chemical shift Ha  3H, n = 0  n+1 = 1 (singlet) Hb  2H, n = 2  n+1 = 3 (triplet) Hc  2H, *n = = 5  n+1 = 6 (sextet) Hd  3H, n = 2  n+1 = 3 (triplet) Ha Hb Hc Hd

Experiment #2: Nucleophilic substitution Given 1 of 3 possible unknown Task: Setup reaction (reflux), vacuum filtration (cold), and melting point Today’s goal: Synthesize product and get melting point value Main goal: Identify the product using NMR, MP, and TLC Remember to save filtrate and product! Part 2 teaser: recrystallization of product and TLC

SN1 or SN2? – SN1  carbocation (3˚ > 2˚ > 1˚) – SN2  steric hindrance (1˚ > 2˚ > 3˚) An easy dump and stir

Reflux (aka add heat) A way to heat the reaction to boiling Condenser with cold water, cools down the vaporizing solvent to minimize loss

Vacuum filtration Separate solids from liquid Liquid = filtrate The negative pressure from the vacuum helps to pull the filtrate through Cold solvents/wash solutions to reduce loss of product due to solubility

Melting point Melting point is a range – Tight/small range is good Melting point depreciates with impurity – The more impurity, the lower your mp (a way to judge purity) Always compare it to the literature MP value – Helps to identify your product Remember: melting point tubes are open at one end and close on the other!