ATENOLOL SPECTRAL DATA

Atenolol 

In order for one to appreciate the spectroscopy for ATENOLOL, one must initially consider its full molecular structure. The simplest means to explore and trace the ATENOLOL's spectroscopic characteristics is to look at its 2D arrangement :

On the outset it is clear that ATENOLOL possesses a multitude of component substituents. The main "bulk" on the molecule is attached to a bulky structure itself, namely the benzene ring.  

such a molecule can be described as a benzeneacetamide by virtue of the O=C-NH2 amide group extruding from a benzene ring. As well as the amide functional group, the conjugating C=C bond in the benzene ring, the methine (CH), methylene (CH2), methyl (CH3) and -OH functional group should be distinctive on the IR spectra (amide circa 1650cm-1 ;CH circa 2880-2900cm-1 ; CH2 circa 2916-2936 cm-1 ; CH3 circa 2850 cm-1 ; conjugating C=Ccirca 1640-1610 ; -OH circa 3200-3550cm-1). 

The mass spectra should theoretically present the molecular ion at 266, being the relative molecular mass of the drug. In relation toATENOLOL's 13-Carbon and 1-Hydrogen nmr, the splitting patterns would be vast, likely to have one pronounced broad peak due to the -OH group. 
The effect of the electronegative oxygen leads to neighbouring hydrogen nuclei being deshielded, moving the coupling peaks downfield whilst also possibly giving rise to hydrogen bonding. The predictions will now be tested, utilising the 2D structure above to explain the various observations which prevail...

The structural formula

UV - spectrum

Conditions : Concentration - 2.4 mg / 100 ml; 12 mg / 100 ml
Solvent designation schedule	Methanol	Water	0.1 M HCl	0.1M NaOH
The absorption maximum	275 nm  227 nm	-	274 nm  225 nm	275 nm
	54  375	-	47.5  349	49
ε	1430  10000	-	One thousand two hundred sixty  9290	1300

IR - spectrum

Wavelength (μm)
Wavenumber (cm -1 )

IR SPECTRA

INFRA RED SPECTRA OF ATENOLOL CONDUCTED ON A KBR DISC

IR FREQUENCY BAND (cm-1)	GROUP RESPONSIBLE
3368	-OH
3198-3071	H-N
2966	C-CH3
2924	CH2
2870	C-H
1666	C=O
1649	O=C-NH2
1614	Conjugated C=C (aromatic)
886	C=CH2

A key observation which is raised in the IR spectrum of ATENOLOL is the level of hydrogen bonding. By virtue of the electronegative Nitrogen atom and the even more electronegative Oxygen atom, the IR spectra indicates that intermolecular H-bonding may be present. This is demonstrated by the IR frequency bands of the -OH and H-N and groups having stretched at 3368cm-1 and 3198-3071 cm-1 respectively. Theoretical values indicate the following ; (a "free" group representing a non H-bonded group) :

IR FREQUENCY BAND (cm-1)	GROUP RESPONSIBLE
3610-3645 (sharp)	Free -OH
3200-3550 (broad)	H bonded -OH
3300-3500	Free -NH
3070-3350	H bonded NH

By simply cross referencing these figures with those obtained from the IR spectrum one is able to establish that hydrogen-bonding is present, as hypothesised in our prediction at the beginning of the section.

MASS Spectrum

Spectrum
The 10 largest peaks:
Peak	30	32	41	43	44	56	57	72	73	107
Meaning	568	61	73	100	52	92	64	999	53	57

Source Temperature: 160 C
Sample Temperature: 140 C
Direct, 75 eV

A TABLE OF THE RESPONSIBLE STRUCTURAL FRAGMETS

m/z	Structural Fragment
266
251
222
134
72
58
44
28

The molecular ion was determined at 266, as predicted. The array of fragments tabulated above encapsulate the diversity of component constituents which structure the ATENOLOLmolecule.

NMR SPECTRUM

1-HYDROGEN NMR

1-H NMR OF ATENOLOL

CONDUCTED @ 399.65 MHz
0.039 g : 0.5 ml CDCl3

Proton	Chemical Shift (ppm)
a	7.41
b	7.158
c	6.855
d	3.84
e	5.00
f	3.91
g	2.539
h	1.50
i	2.68
j	0.970
k	0.975
l	6.85
m	3.285

There are a few key inferences that can be made from the data acquired. Proton a is bonded to Nitrogen, a fairly potent electronegative atom (3.04 Pauling units). The N-H bond is thus slightly polarised with the Nitrogen atom drawing the hydrogen's electron towards it. The nature of this bond means that Proton a becomes deshielded thereby making it extremely acidic. The net effect is that the 1-H nmr displays the proton vastly downfield in relation to its counterparts. 
For comparative purposes, it is clear that Proton's j and k are shielded rather well by virtue of their extreme upfield positions. They exhibit integration, being in the same environment shown as the largest peak on the spectra. As well as Proton a, Proton c experiences deshielding even though not being directly bonded to the electronegative species. The atom responsible is now the extremely electronegative Oxygen atom (3.44 Pauling units). Despite its distance, the pair of protons experience deshielding by virtue of oxygen's potent electron withdrawing affect. 
As predicted, Proton e is isolated as a single broad peak not coupling with neighbouring atoms, being attached to the electronegative Oxygen atom. Coupling is displayed, pronounced forProtons i whereby it is able to couple with Protons k and j, evolving a doublet of quartets.

13-CARBON NMR

13-C NMR OF ATENOLOL

CONDUCTED @ 22.53 MHz
0.039 g : 0.5 ml DMSO-d6

Carbon	Chemical Shift (ppm)	Intensity
1	172.52	366
2	157.27	440
3	129.88	967
4	128.31	477
5	114.17	946
6	70.81	361
7	68.35	478
8	49.96	394
9	48.09	553
10	41.31	285
11	22.88	1000

Similar inferences can be made for the 13-Carbon nmr, with the electronegative oxygen showing obvious electronegative potency with Carbon 1 being shifted extremely downfield this time being assisted with the largely electronegative Nitrogen atom as well. The net effect is a highly polarised delta positive carbon atom.


[1H,13C] 2D NMR Spectrum





MORE OF 1H NMR

Links

• UV and IR Spectra. H.-W. Dibbern, RM Muller, E. Wirbitzki, 2002 ECV
• NIST / EPA / NIH Mass Spectral Library 2008
• Handbook of Organic Compounds. NIR, IR, Raman, and UV-Vis Spectra Featuring Polymers and Surfactants, Jr., Jerry Workman.Academic Press, 2000.
• Handbook of ultraviolet and visible absorption spectra of organic compounds, K. Hirayama. Plenum Press Data Division, 1967.
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