|
| C-13 NMR
Shifts for 4-Androstene-3,17-dione
|
|
Introduction -- Chemists
that use C-13 NMR for organic molecular structure analysis need
accurate chemical shift predictions. NMRPen combines a database
of more than 73000 assigned chemical shifts with proven NMR shift
predictions methods to make NMR shift predictions. To estimate a
set of shifts a user draws the chemical structure, then selects
the NMR Shifts menu item. Within seconds a set of shifts computed
and displayed. NMRPen also includes ChemPen3D
for molecular mechanics.
|
|
How does NMRPen work? --
NMRPen encodes each atom's local electronic and connective
environment into unique number codes. Each assigned chemical
shift is matched with a unique code set. NMRPen's database
contains more than 73,000 shift/code entries. To make a
prediction NMRPen computes the codes for an atom then searches
for a match in the database. Absent exact or partial matches
NMRPen combines a variety of known NMR Shift prediction
algorithms with the database shifts to compute the estimated
shifts. References
|
| Is NMRPen fast? -- This will
depend on the speed of your computer and the current state of the
NMRPen shift library. On an older 75MHz Pentium® estimating the
19 shifts of Androstenedione required less than two seconds.
Predictions will be faster for molecules with many exact matches
and for highly symmetrical molecules.
|
|
How Accurate is NMRPen? --
Because NMRPen combines a database with several empirical methods
accuracy is hard to predict analytically. Our empirical testing
indicates NMRPen a typical NMR shift prediction will be within 3
ppm of the experimental value on average.
|
| What is encoding? -- Encoding is
numerical representation of an atom's environment using a simple
set of simple rules. The number of encoding schemes is virtually
infinite. NMRPen's model was inspired by molecular connectivity analysis
and includes atom types, hybridizations, bonds and charges.
NMRPen's encoding scheme is not limited to tabulating chemical
shifts.
|
|
Can I add my own shifts? --
Yes. To add your own shifts, draw your chemical structure then
select NMR Shifts to launch the NMR tool. A set of predicted shifts are
generated. Enter your own shifts, if needed in the Add Shift
window.
|
| System Requirements -- NMRPen
runs on Windows 98,NT,2000,XP,Vista®. Recommended minimum
requirements are a Pentium , 32MB for Windows® 9X, 64MB for
Windows NT,2000, XP®, 8MB free HDD. As with all versions of
Windows® more memory is better. For email delivered versions:
Microsoft Installer Engine installed(It's usually present).
|
|
Click below to purchase NMRPen NMRPen is $199+S&H Secure credit card services by Northstar,Solutions Inc,® ChemPen©, ChemPen3D©, NMRPen © 2010
|
