Ethylene conjugate base

Where do hydrocarbons lie on the acidity scale As the data in Table 8.1 show, both methane (pKa 60) and ethylene (plC, = 44) are very weak acids and thus do not react with any of the common bases. Acetylene, however, has piCa = 25 and can be deprotonated by the conjugate base of any acid whose pKa is greater than 25. Amide ion (NH2-), for example, the conjugate base of ammonia (pKa - 35), is often used to aeprotonate terminal aikynes. 

The alkane propane has pATa 50, yet the presence of the double bond in propene means the methyl protons in this alkene have pATa 43 this value is similar to that of ethylene (pATa 44), where increased acidity was rationalized through sp hybridization effects. 1,3-Pentadiene is yet more acidic, having pATa 33 for the methyl protons. In each case, increased acidity in the unsaturated compounds may be ascribed to delocalization of charge in the conjugate base. Note that we use the term allyl for the propenyl group. 

CHES 3-(Cyclohexylamino)ethanesulfonic acid EGTA Ethylene glycol bis(/3-aminoethyl ether)-A,A,A, A -tetraacetic acid or its conjugate base... 

The presence of an bond also makes a compound a base. With this in mind, draw the conjugate acid of ethylene. CH2=CH2. What is ethylene s conjugate base ... 

The conjugate bases formed by removing a proton from ethane, ethylene, and acetylene are each carbanions—species with a negative charge on carbon. 

Table 1. Trienes used in the synthesis of ethylene-propylene based terpolymers containing conjugated diene systems... 

Write the ionization reaction of aniline, CeHjNHa, in glacial acetic acid, and identify the conjugate acid of aniline. Write the ionization reaction of phenol, CgHsOH, in ethylene diamine, NH2CH2CH2NH2, and identify the conjugate base of phenol. 

Recall that a lower piT corresponds to a greater acidity. Therefore, acetylene (piT = 25) is significantly more acidic than ethane or ethylene. To be precise, acetylene is 19 orders of magnitude (10,000,000,000,000,000,000 times) more acidic than ethylene. The relative acidity of acetylene can be explained by exploring the stability of its conjugate base, called an acetylide ion (the suffix ide indicates the presence of a negative charge) ... 

The stability of an acetylide ion can be rationalized using hybridization theory, in which the negative charge is considered to be associated with a lone pair that occupies an s -hybridized orbital. Compare the conjugate bases for ethane, ethylene, and acetylene (Figure 10.3). 

The conjugate base of ethane exhibits a lone pair in an sp -hybridized orbital. The conjugate base of ethylene has the lone pair in an sp -hybridized orbital, and the conjugate base of acetylene has the lone pair in an sp-hybridized orbital. 

Now, let s draw out the forward scheme. This multi-step synthesis uses three equivalents of ethylene (labeled A, B, C in the scheme below) and one equivalent of acetic acid (labeled D). Ethylene (A) is converted to 1,2-dibromoethane upon treatment with bromine. Subsequent reaction with excess sodium amide produces an acetylide anion which is then treated with bromoethane [made tfom ethylene (B) and HBr] to produce 1-butyne. Deprotonation with sodium amide, followed by reaction with an epoxide [prepared by epoxidation of ethylene (C)] and water workup, produces a compound with an alkyne group and an alcohol group. Reduction of the alkyne to the cis alkene is accomplished with H2 and Lindlar s catalyst, after which the alcohol is converted to a tosylate with tosyl chloride. Reaction with the conjugate base of acetic acid [produced by treating acetic acid (D) with NaOH] allows for an Sn2 reaction, thus yielding the desired product, Z-hexenyl acetate. 

Conjugation as well as geometric and positional isomerization occur when an alkadienoic acid such as linoleic acid is treated with a strong base at an elevated temperature. CycHc fatty acids result from isomerization of linolenic acid ia strong base at about 250°C (58). Conjugated fatty acids undergo the Diels-Alder reaction with many dienophiles including ethylene, propylene, acryUc acid, and maleic anhydride. 

In the Diels-Alder reaction a double bond adds 1,4 to a conjugated diene (a 2 + 4 cycloaddition), so the product is always a six-membered ring. The double-bond compound is called a dienophile. The reaction is easy and rapid and of very broad scope and reactivity of dienes and dienophiles can be predicted based on analysis of the HOMOs and LUMOs of these species. Ethylene and simple alkenes make poor dienophiles, although the reaction has been carried out with these compounds. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

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