isobutane structural formula
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The structural formula of a chemical compound is a graphical representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly. There are several common representations used in publications. These are described below. Also several other formats are used, as in chemical databases, such as SMILES, InChI and CML.
Unlike chemical formulas or chemical names, structural formulas provide a representation of the molecular structure. Chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the changes that occur.
Many chemical compounds exist in different isomeric forms, which have different structures but the same overall chemical formula. A structural formula indicates the arrangements of atoms in a way that a chemical formula cannot.
Lewis structures (or "Lewis dot structures") are flat graphical formulas that show atom connectivity and lone pair or unpaired electrons, but not three-dimensional structure. This notation is mostly used for small molecules. Each line represents the two electrons of a single bond. Two or three parallel lines between pairs of atoms represent double or triple bonds, respectively. Alternatively, pairs of dots may used to represent bonding pairs. In addition, all non-bonded electrons (paired or unpaired) and any formal charges on atoms are indicated.
In early organic-chemistry publications, where use of graphics was severely limited, a typographic system arose to describe organic structures in a line of text. Although this system tends to be problematic in application to cyclic compounds, it remains a convenient way to represent simple structures:
Parentheses are used to indicate multiple identical groups, indicating attachment to the nearest non-hydrogen atom on the left when appearing within a formula, or to the atom on the right when appearing at the start of a formula:
(CH3)2CHOH or CH(CH3)2OH (2-propanol)
In all cases, all atoms are shown, including hydrogen atoms.
Skeletal formulas are the standard notation for more complex organic molecules. First used by the organic chemist Friedrich August KekulÃ© von Stradonitz the carbon atoms in this type of diagram are implied to be located at the vertices (corners) and termini of line segments rather than being indicated with the atomic symbol C. Hydrogen atoms attached to carbon atoms are not indicated: each carbon atom is understood to be associated with enough hydrogen atoms to give the carbon atom four bonds. The presence of a positive or negative charge at a carbon atom takes the place of one of the implied hydrogen atoms. Hydrogen atoms attached to atoms other than carbon must be written explicitly.
Indication of stereochemistry
Several methods exist to picture the three-dimensional arrangement of atoms in a molecule (stereochemistry).
Stereochemistry in skeletal formulas
Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example the diagram below shows the fructose molecule with a wavy bond to the HOCH2- group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure. The ring continually opens and closes, sometimes closing with one stereochemistry and sometimes with the other.
Newman projection and sawhorse projection
The Newman projection and the sawhorse projection are used to depict specific conformers or to distinguish vicinal stereochemistry. In both cases, two specific carbon atoms and their connecting bond are the center of attention. The only difference is a slightly different perspective: the Newman projection looking straight down the bond of interest, the sawhorse projection looking at the same bond but from a somewhat oblique vantage point. In the Newman projection, a circle is used to represent a plane perpendicular to the bond, distinguishing the substituents on the front carbon from the substituents on the back carbon. In the sawhorse projection, the front carbon is usually on the left and is always slightly lower:
Certain conformations of cyclohexane and other small-ring compounds can be shown using a standard convention. For example, the standard chair conformation of cyclohexane involves a perspective view from slightly above the average plane of the carbon atoms and indicates clearly which groups are axial and which are
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Answers:Alkyl group is an alkane missing one hydrogen atom, the formula is CnH2n+1 H3C-CH2-CH2-CH3 is buthane (C$H10) and alkyle would be C4H9- structure is H3C-CH2-CH2-CH2- Isopropyl H3C-CH-CH3 *******************/ Isobutane H3C-CH-CH3 *****/ ****CH3
Answers:Alkanes with more than three carbon atoms can be arranged in a multiple number of ways, forming different structural isomers. An isomer is like a chemical anagram, in which the atoms of a chemical compound are arranged or joined together in a different order. The simplest isomer of an alkane is the one in which the carbon atoms are arranged in a single chain with no branches. This isomer is sometimes called the n-isomer (n for "normal", although it is not necessarily the most common). However the chain of carbon atoms may also be branched at one or more points. The number of possible isomers increases rapidly with the number of carbon atoms (sequence A000602 in OEIS). For example: C1: 1 isomer methane C2: 1 isomer ethane C3: 1 isomers propane C4: 2 isomers n-butane, isobutane C12: 355 isomers C32: 27,711,253,769 isomers C60: 22,158,734,535,770,411,074,184 isomers In addition to these isomers, the chain of carbon atoms may form one or more loops. Such compounds are called cycloalkanes. As such there is no mathematical formula for determining the number of isomers for an alkane.
Answers:The formulas for acetaldehyde is incomplete, and the one for acetophenone (methyl phenyl ketone) doesn't show the full structure, with the benzene ring. acetaldehyde is H CCH=O acetophenone is H CC=O attached to a ring that can only be drawn using HTML (which I doubt Yahoo allows), but it consists of 6 carbons connected in a ring by bonds of multiplicity 1.5 (the resonance form combining two canonical forms of alternating single and double), with each but the one at the carbonyl attached to a hydrogen atom. I don't know if you wanted that kind of detail, or rather if your teacher or prof did, but you got it anyway. :) ---------------------------------------------------------------- Actually, there is a way for me to show you the structure of acetophenone (both the resonant representation and the canonical form): http://hspost.com/acetophenone.gif
Answers:Google "polypeptide structure"