Methyl carbons, attached proton test

The other experiment worth mentioning, which, by the way, is also obsolete, is the attached proton test or APT. This experiment is based on the different magnitudes of Tl—13C coupling for methine, methylene, and methyl groups. By adjusting certain delays in the pulse sequence (not given), quaternary and methylene carbons could be phased up, and methine and methyl carbons could be phased down. Since phase is arbitrary, this order could be reversed. This ability of distinguishing... 

Previously, it was reported that the chemical shift of the proton atoms of the C-12 of the fatty acid methyl ester can be found at 3.503 ppm (50). In the HMBC-NMR spectrum, there is a cross peak between this proton of C-12 and the carbon atom with a chemical shift of 95.23 ppm. This is a tertiary carbon atom. The discrimination between quaternary and tertiary C signals has been performed by using an attached proton test (APT) pulse sequence, one each second. The cross peak refers to the three-bond coupling of the H-12 protons with the anomeric center C-1 of lactose. The H-data of C-1 were found with the one-bond coupling constant, which is 150 MHz. With a COSY-NMR spectrum and its corresponding HMBC spectrum, the H and C NMR values of C-2, C-3, could be determined. 

The NMR spectrum of the pure hydroxypropylated polystyrene showed peaks in the regions of d 21.5-26 ppm and d 64-67.5 ppm. Analysis by the attached proton test (APT) in conjunction with model compounds indicated that the region between 21.5 and 26 ppm corresponds to the methyl carbon resulting from attack of the polymeric organo-lithium at the least hindered carbon to form a secondary alcohol chain-end functional group (see (a) in eqn [7]). The area between 3 64 and 67.5 ppm was assigned to the carbon bonded to oxygen for two diastereomerically different products as shown by structure 1, where the chiral carbon atoms are labeled with asterisks. 

From C-NMR spectroscopy, an attached proton test, and C COSY, we know that SIF contains a carbonyl (177 ppm), three aromatic carbons (131 and 134 ppm) only one of which is protonated (142 ppm), a CH group (64 ppm the "X proton), and a methylene group (at 35 ppm) which interacts with the aromatic carbons and is coupled to the CH carbon, and a methyl group at 26 ppm. The nature of two other carbons has not yet been resolved. 

The NMR spectrum of polymer 3e was run as an attached proton test (APT). This spectrum shows the methyl carbons appearing as a downward peak at 30.39 ppm and the quaternary carbon of the isopropylidene group as an upward peak at 41.83 ppm. The cyclopentadienyl resonance appears at 77.74ppm as an intense peak pointing down. The complexed aromatic CH carbons appear at 74.76 ppm, while... 

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