# What is coupling constant J?

## What is coupling constant J?

The coupling constant, J (usually in frequency units, Hz) is a measure of the interaction between a pair of protons. In general, the more bonds involved between the H that are coupling, the smaller the J value.

What is the expected coupling constant?

The coupling constant is simply the difference, expressed in Hz, between two adjacent sub-peaks in a split signal. For our doublet in the 1,1,2-trichloroethane spectrum, for example, the two subpeaks are separated by 6.1 Hz, and thus we write 3Ja-b = 6.1 Hz.

### How do you find the coupling constant?

The Karplus equation describes how the coupling constant between two protons is affected by the dihedral angle between them. The equation follows the general format of J = A + B (cos θ) + C (cos 2θ), with the exact values of A, B and C dependent on several different factors.

What is the coupling constant J value for Cs isomer?

If it is a trans the J-Coupling constant of the unsaturated protons in the spectrum shows nearly 13-16 Hz, and it is nearly 10-12 in case of Cis isomers.

## What affects coupling constant?

The major factors affecting coupling constants are dihedral angles, substituents, hybridization, and ring strain.

What is fluorine coupling?

Coupling between hydrogen and fluorine (spin 1/2) is very strong. Typical 2J coupling constants are about 48 Hz. Longer range coupling is smaller. Typical 4J coupling constants are about 4 Hz. The nuclear spin of fluorine is 1/2.

### What is the coupling constant between carbon and fluorine?

Coupling between carbon and fluorine (spin 1/2) is very strong. Typical 1J coupling constants are about 185 Hz. Longer rangecoupling is smaller. Typical 2J coupling constants are about 20 Hz.

How are the coupling constants of benzotrifluorides determined?

The carbon–fluorine coupling constants in 33 different substituted benzotrifluorides (trifluoromethyl‐benzenes) have been determined. The 3J (CF) to the ortho aromatic ring carbons varied between 1.7 and 5.6 Hz and, in a given molecule, were always larger than the 5J (CF) to the para carbon, which ranged between 0.7 and 1.7 Hz.

## What are the coupling constants for sp 2 carbons?

With protons bound to sp 2 -hybridized carbons, coupling constants can range from 0 Hz (no coupling at all) to 18 Hz, depending on the bonding arrangement. For vinylic hydrogens in a trans configuration, we see coupling constants in the range of 3J = 11-18 Hz, while cis hydrogens couple in the 3J = 6-15 Hz range.

What is the coupling constant for CF3 carbon?

If we have to report a CF3 functional group containing a compound, then what is the range of the J value (coupling constant) in a 13C-NMR for CF3 carbon and carbon ‘attached to’ CF3 in simple aromatic ring system? Join ResearchGate to ask questions, get input, and advance your work.