Heteroatom An atom other than

An annulene is a monocyclic hydrocarbon with alternating single and double bonds. A heterocyclic compound is a cyclic compound in which one or more of the ring atoms is a heteroatom—an atom other than carbon. Pyridine, pyrrole, furan, and thiophene are aromatic heterocyclic compounds. 

Heteroatom An atom other than C or H in an organic molecule the most common heteroatoms are O, N, S, P, and the halogens. 

For which compounds containing a heteroatom (an atom other than carbon or hydrogen) does the molecular ion have an even-numbered mass For which does it have an odd-numbered mass ... 

HETCOR spectrum a 2-D NMR spectrum that shows coupling between protons and the carbons to which they are attached, heteroatom an atom other than carbon or hydrogen. 

Not all cyclic compounds are hydrocarbons Many substances include an atom other than carbon called a heteroatom (Section 1 7) as part of a ring A ring that contains at least one heteroatom is called a heterocycle, and a substance based on a heterocyclic ring is... 

Hetero-Diels-Alder products (i.e., Diels-Alder products involving an atom other than carbon) have also been observed for a number of systems at the Si(100)-2 x 1 surface. Some examples include the reaction of unsaturated ketones RC=C—CR=0 (e.g., ethylvinylketone) [255], 2-propenenitrile [256-260], and dicarbonyls 0=C—R—C=0 [261]. For a review specifically of heteroatom chemistry at the silicon surface, the reader is referred to Ref. [262]. Here we use the dicarbonyl example to provide an illustration of this class of surface chemistry. Hamers and coworkers have used the [4 + 2] heteroatom cycloaddition reaction of... 

Heteroatom Any atom other than carbon or hydrogen in an organic molecule. 

Any ring system containing at least one heteroatom (i.e. an atom other than carbon - typically nitrogen, oxygen, or sulphur) can be described as heterocyclic. This broad definition encompasses both aromatic heterocycles (such as pyridine 5.1) and their non-aromatic counterparts (piperidine 1.7). 

Heteroatom (Section 3.1) An atom other than carbon or hydrogen. Common heteroatoms in organic chemistry are nitrogen, oxygen, sulfur, phosphorus, and the halogens. 

Some amines are heterocyclic compounds (or heterocycles)—cyclic compounds in which one or more of the atoms of the ring are heteroatoms. A heteroatom is an atom other than carbon. The name comes from the Greek word heteros, which means different. A variety of atoms, such as N, O, S, Se, P, Si, B, and As, can be incorporated into ring stmctures. 

Some amines are heterocyclic compounds—cyclic compounds in which one or more of the atoms of the ring is an atom other than carbon. Heterocyclic rings are numbered so that the heteroatom has the lowest possible number. A natural product is a compound synthesized by a plant or an animal. Alkaloids are natural products containing one or more nitrogen heteroatoms and are found in the leaves, bark, roots, or seeds of plants. 

From an organic chemist s viewpoint, heteroatoms are atoms other than carbon or hydrogen that may be present in organic compounds. The most common heteroatoms are oxygen, nitrogen, and sulfur. In heterocychc compounds, one or more of these heteroatoms replaces carbon in a ring. 

Aromatic rings can also contain heteroatoms. Pyridine, C5H5N, for example, is a six-membered ring nitrogen heterocycle (contains an atom other than carbon in the ring). Like benzene, each atom of the ring is sp hybridized, and... 

Hess s law phys chem The law that the evolved or absorbed heat in a chemical reaction is the same whether the reaction takes one step or several steps. Also known as the law of constant heat summation. hes-oz, 16 hetero- chem Prefix meaning different for example, a heterocyclic compound is one in which the ring is made of more than one kind of atom. hed-o-ro heteroatom org chem in an organic compound, any atom other than carbon or hydrogen. hed-3-ro,ad-3m ... 

Cyclic ethers are our first examples of heterocyclic compounds, containing a ring in which a ring atom is an element other than carbon. This atom, called the heteroatom, is numbered 1 in numbering the ring atoms. Heterocyclic ethers are especially important and useful ethers. 

The exception occurs when we are dealing with a H on a that is sp hybridized in this case, the HMBC cross peak between a bound to an s/r -hybridized carbon and an adjacent will be weak or may even be absent, although the cross peak between a H and a three bonds away will likely be intense. The absence of the HMBC cross peak between a H on an sp -hybridized carbon and an adjacent C stems from the fact that a geminal bond angle of 120° (caused by the sp hybridization) gives a smaller —usually less than 2 Hz. The presence of a heteroatom near the C two bonds from the H in question maybe sufficient to disrupt the conditions that drive the to near zero hence, the presence of atoms other than H and C may favorably influence HMBC cross peak intensity between H s bound to sp -hybridized carbons and C s two bonds distant. 

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