DAT IR Spectroscopy Notes

n+1 rule HNMR

if a proton has n protons that are three bonds away, it will be split into n+1 peaks

C-NMR Alkanes, Alkenes, aromatic compounds

increase in ppm in that order, becoming more and more positive fall within 0-70, 90-12, 110-160 ppm regions

H-NMR Spectroscopy

Just as with 13C-NMR, if two different hydrogens are in exactly the same environment- that is, they have the EXACT same stuff all around them in all directions- then they are the "same kind of" or "equivalent" hydrogens. The number of peaks (signals) we see on our H-NMR spectrum will equal the number of non-equivalent (different) hydrogen atoms in our molecule

CN

Medium peak ~2200

What type of molecules cannot give an IR spectrum?

Molecules with no net dipole

Can find what is most likely to form a weight m/z by

finding a total subs weight that matches. If all the answers have the same weight, see which one is more internally stable

The positively charged an individual hydrogen is, the ________ it will appear on a 1H spectrum

further to the left Further to the left, more downfeild, more "de-sheilded" = more positive

The more positively charged an individual carbon is, the ________ it will appear on an 13C spectrum

further to the left The more left, the more downfield, the more "de-shielded" = more positively charged

The more negatively charged an individual atom is, the ______ it will appear on a 1H spectrum

further to the right Further to the right, more upfield, more "shielded" = more negative

The more negatively charged, the_______ it will appear on an 13C spectrum

further to the right The more right, the more up-field, the more "shielded" = more negatively charged

The number of shifts a compound gives in its 1H NMR spectrum is equal to

the number of sets of non-equivalent protons Count shifts of the HNMR spectrum to discover compound

Aldehydes Hs HNMR

~10 ppm

Phenol Hs HNMR

~10 ppm

C-H (sp) (sp2) (sp3)

~3000 sp is the the left of sp2 which are left of sp3 sp<sp2<sp3

Trick in counting hydrogen in HNMR involving double bonds

Since double bonds do not rotate freely, you must count the Hs directly on a double/triple as their own because they are stick in their position

# of degrees of unsaturation

Spaces where hydrogens could be Degree of Unsaturation = C - (H/2) - (X/2) + (N/2) +1

The most stable ion in the entire mix of possible fragments in Mass Spectroscopy is...

The fragment with the tallest peak (base peak)

Integrals of HNMR

The integral numbers above each peak tell you how many hydrogens are in that peak

How do you know how many signals will be in a C-NMR?

The number of "different" unique carbons that are connected to different things

base peak (mass spec)

The tallest peak does not necessarily correspond to the molecules molecular mass peak (M peak), or the parent peak Only tells you which one of the fragments is the most stable, most abundant fragment

Molecular Ion (M) "parent peak"

The whole molecule that has electron attached to it (no pieces are detached)

Finger Print region

To the right of the C=O bond (1700) but you can pretty much ignore it

UV-Vis spectroscopy

Use a UV/Vis spectrometer with a compound, where it is bombarded in sequence by UV and visible light. Mostly used to analyze compounds with conjugated double bonds

NO2

Vampire teeth at 1500-1600 and 1300-1400

Mass Spectrometry

a technique that separates particles according to their mass Mostly used to determine a compound's mass

Hs stuck to aromatic rings like benzene HNMR

6-8 ppm

C-NMR Aldehydes, ketones

>200 ppm

OH (not carboxylic acid)

A LARGE, broad trough before C-H before ~3000

Mass to charge ratio

A way peaks (fragments) are separated in mass spec

N-H (NH) (NH2)

3500-3200 Sharp Peak one peak for NH two peaks for NH2

Hs stuck to a c=c bond HNMR

4-6 ppm

TMS HNMR

0 (not apart of compound)

C-NMR TMS

0 ppm (not apart of compound in C-NMR)

Alcoholic OHs HNMR

0.5-5.5 ppm

Amine NHs

0.5-5.5 ppm

Single bonded hydrogens (sp3 hybridized) HNMR

1-5 ppm

Carboxylic acid Hs HNMR

10-12 ppm

Amide Hs HNMR

11-13 ppm

C-NMR Esters, amides, and carboxylic acids

160-180 ppm

C=O

1700 (+/-) 50 huge peak

Two motions that can occur

Bond Stretching, Bond bending.

Higher wavenumber =

Higher-energy bond movement

Splitting in HNMR

Hydrogens atoms get split by neighboring hydrogens. TO figure out the splitting, count all the hydrogens next-door in all directions and add 1 (n+1)= number of peaks in that will be in that integral of hydrogens INTEGRAL: how many Hs there are SPLIT: tells how many hydrogens are next door

IR Spectroscopy

is one tool we use to determine molecule's structures. IR spectroscopy works because all bonds wiggle in different ways when you shoot IR light at them. The energy left over ( the energy that doesn't get absorbed by the molecules) can be turned into something called an IR spectrum

OH (carboxylic acid)

on top of C-H bond 3300-2500