Chains, carbon atoms straight

Figure 4. Effect of methyl substitution on relative burning velocities of four-carbon-atom, straight-chain hydrocarbons (30)...

Prior to the elucidation of the structure of the gypsy moth natural attractant, we tested about 2000 synthetics against this insect. Both the isolation and synthesis approaches were being explored. Several attractive compounds were turned up (69). Not so surprisingly, the attractive structures were later found to be similar to the natural attractant, in that they were 16-carbon-atom straight-chain compounds with a primary alcohol group, or at least a potential primary alcohol (epoxy) group. 

In addition to linking in long straight chains, carbon atoms also form branched structures. For example, we saw earlier that butane (C4HJ0) has the following structure ... 

Aliphatic Containing chains of carbon atoms (straight or branched), rather than rings. Aliphatic compounds may be saturated or unsaturated. 

The fatty acids occur in nature chiefly as glycerides see fats), which constitute the most important part of the fats and oils, and as esters of other alcohols, the waxes. The naturally occurring fatty acids are mostly the normal straight-chain acids with an even number of carbon atoms. 

The rings most frequently encountered in crude oils are those having five or six carbon atoms. In these rings, each hydrogen atom can be substituted by a paraffinic alkyl chain that is either a straight chain or branched. 

Other investigations dealt with straight-chain molecules (oi-tricosenoic acid) in which the penultimate and final carbon atoms at the hydrophobic end are connected by a double bond [91, 92]. The material does not polymerize as rapidly as those described before when irradiated by UV light, however, but it is readily polymerized when bombarded with an electron beam. It was thus thought to be an optimal material for the fabrication of electron beam resists. 

We shonld also utilize liquid hydrocarbons, which frequently accompany natural gas. These so-called natural gas liquids currently have little use besides their caloric heat value. They consist mainly of saturated straight hydrocarbons chains containing 3-6 carbon atoms, as well as some aromatics. As we found (Chapter 8), it is possible by superacidic catalytic treatment to upgrade these liquids to high-octane, commercially usable gasoline. Their use will not per se solve our long-... 

In this case the longest continuous chain has five carbon atoms the compound is named as a derivative of pentane The key word here is continuous It does not matter whether the carbon skeleton is drawn m an extended straight chain form or m one with many bends and turns All that matters is the number of carbons linked together m an uninterrupted sequence... 

Should there be a choice for the fundamental straight chain of a radical, that chain is selected which contains (1) the maximum number of double and triple bonds, (2) the largest number of carbon atoms, and (3) the largest number of double bonds. These are in descending priority. 

Formic acid is the most acidic straight-chain alkanoic acid. SolubiUty in water of alkanoic acids containing more than nine carbon atoms is too low... 

The system for naming the straight-chain hydrocarbons is based on an agreed-upon method of retaining the first three or four common names, then using Greek prefixes that indicate the number of carbon atoms in the chain. For isomers, the same system is used, always using the name of the compound that is attached to the chain and the name of the chain. 

Branched-chain alkanes, also known as isoparaffins or isoalkanes, are possible when n > 4. The prefix iso is used when two methyl groups are attached to a terminal carbon atom of an otherwise straight chain and the prefix neo when three methyl groups are attached in that manner. Branched-chain alkanes are sometimes regarded as normal alkanes with attached substituent alkyl groups. An example is... 

The oxidation described here was performed in 80% (v/v) acetonitrile — 20 % water (mole fraction of water = 0.42) at 35.0 °C. Figure 2 shows the selectivity as a function of the number of carbon atoms in R2. In the case of oxidation of la and 2a (R2 = branched alkyl groups), the selectivity reaches a sharp maximum (r = 2.4) at the isopentyl group (j = 2)l8). For R2 = straight-chain alkyl groups, alternation in the selectivity is clearly observed 18). The difference between the r value for la and 2a2 and that for la and 2h2 reaches up to 3.7. 

In connection with the Webb and Levy test, it should be mentioned that this test can also be applied to the estimation of all 2-deoxy aldoses, including those containing a terminal deoxy group, provided they have at least five carbon atoms in a straight chain 2-deoxy tetroses do not react (62). It has also been used for the estimation of 3-deoxy and 3, 6-di-deoxy hexoses, after their conversion to the corresponding 2-deoxy pentoses by removal of carbon 1 with periodate (24,25). 

Straight-chain alkanes are named according to the number of carbon atoms they contain, as shown in Table 3.3. With the exception of the first four compounds—methane, ethane, propane, and butane—whose names have historical roots, the alkanes are named based on Greek numbers. The suffix -one is added to the end of each name to indicate that the molecule identified is an alkane. Thus, pentane is the five-carbon alkane, hexeme is the six-carbon alkane, and so on. We ll soon see that these alkane names form the basis for naming all other organic compounds, so at least the first ten should be memorized. 

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