IR and NMR

What is the fingerprint region?

600-1400cm-1

lots of C-C bonds

stay away from this

low frequency (low energy)

Basic chart for IR

Double bond region

C=O

C=N

C=C

1500-2000cm-1

Triple bond region

2000-2500cm-1

Bonds to H

O-H

N-H

C-H

H is a smaller atom (so lighter), therefore vibrates at a higher frequency (high energy)

IR : alkanes

C-H stretch sp3

2800cm-1 to 3000cm-1

multiple peaks

Alkenes

C=((C-H))

sharp peak after 3000cm-1

low to medium strength

C=C

sharp peak at 1600-1680cm-1

low to medium strength

Alkynes

((H-C))-triple bond-C

3200cm-1 to 3300cm-1

very sharp (due to the carbon hydrogen stretching)

show up as one normally and not a pair

C-H

called terminal alkyne (at the end of the carbon chain)

C-triple bond-C

2100cm-1 to 2260cm-1

Aromatics

C-H bonds off the ring in aromatics

show up as pair of sharp peaks

Ethers MUST KNOW

C-O-C

fingerprint reigon

1050-1150 cm-1

VERY strong peaks

Alcohols

Strong, BROAD O-H stretch from 3200-3400 cm-1

C-O

Similar to ethers, 1050-1260 cm-1

Amines - primary

N-H stretch for NH2, looks like a cowlick (2 little peaks)

3200 to 3500 cm-1

R1NH2

Amines - secondary 

N-H band for R2NH1

3200 to 3500 cm-1

single sharp peak

Review shapes above 3000 cm-1

O-H: strong & broad U shape peak

C-triple bond-C-H: sharp spike

primary amine, R1NH2, (N-H): W shape

secondary amine, R2NH1 (N-H): medium V shape peak

C=C-H: small peak shouldered above 3000 cm-1

Aldehyde

C=O (carbonyl) stretch from 1720-1740 cm-1

highly unique sp2 C-H appears of alkanes (2720-2820)

if you have an aldehyde, look for the doublet off the alkane, if there ISNT, it is a ketone

Ketones

C=O stretch occurs at 1705-1725 cm-1

very similiar to aldehydes LOOK FOR THE DOUBLET, if there is none off the alkane or at the 2700-2800 cm-1 region, it is a ketone

esters

C=O stretch at 1735-1750 cm-1

strong band for C-O at a higher frequency than ethers or alcohols at 1150-1250 cm-1

Carboxylic Acid

Messiest IR spectra

C=O band occurs between 1700-1725 cm-1

O-H has a broad band from 2400-3500 cm-1

Nitriles

C-triple bond-N

2100 to 2280 cm-1

peak is much more intense than alkyne

H NMR

EWG shift your signal to higher ppm (downfield)

EWG deshield’s your signal

n+1 rule for HNMR

count the adjacent/neighbor hydrogens, then add +1 to it, this will tell you how many peaks show up.

How many peaks are there for A, B and C

(A)CH3-O-(B)CH3-(C)CH2

A - 1 peak (0 hydrogens on O +1)

B- 3 peaks (2 hydrogens +1)

C- 4 peaks (3 hydrogens +1)

Alkanes

Alkenes

Alkynes

Aromatics

Ethers (must memorize shape since its in fingerprint region)

Alcohols

Amine - primary

Amine - secondary

memorize these shapes for above 3000cm-1

aldehydes

ketone

esters (also must memorize shapes since it is apart of fingerprint region)

carboxylic acid 

acid anhydride (may not come up havent seen it yet, just memorize incase)

Amides

-primary (R1NH2): doublet peak shows up at 3200-3500cm-1 

-secondary (R2NH1): single sharp peak shows up at 3200-3500cm-1