20THE ROLE OF PROTECTIVE GROUPS IN ORGANIC SYNTHESIS
20有机合成中保护基团的使用
If a satisfactory protective group has not been located,the chemist has a number of alternatives:rearrange the order of some of the steps in the synthetic scheme so that a functional group no longer requires protection or a protective group that was reactive in the original scheme is now stable;redesign the synthesis,possibly making use of latent ,a functional group in a precursor ,anisole as a precursor of cyclohexanone).Or,it may be necessary to include the synthesis of a new protective group in the overall plan.
如果不到符合要求的保护基，化学家仍然具有大量可供选择的方法：重新安排合成系统中一些步骤的顺序，保证官能团不再需要保护或者在原来的系统中的活性保护基现在变得稳定；可能利用潜在的功能重新设计合成（也就是功能性基团以前驱体形式出现；例如：茴香醚作为环己酮的前驱体）。或者，有必要在总体计划中包括新保护基的合成.
22POLYMERS
22聚合物
The process by which small molecules undergo multiple combinations to form macromolecules is polymerization.Small molecules from which a macromolecule or polymer can be made are called monomers.Two types of polymerization are recognized: (1)condensation polymerization and(2)addition polymerization.A polymer-forming reaction involving elimination of a small molecule such as water or alcohol between monomer units is described as condensation polymerization.In addition polymerization, unsaturated or cyclic molecules add to each other without elimination of any portion of the monomer molecule.The empirical formula of the polymer is then,of course,the same as that of the monomer.
小分子进行多重结合形成大分子的过程叫做聚合反应。组成大分子或聚合物的小分子叫单体。现在有两类公认的聚合反应：（1）缩合聚合（缩聚）反应和（2）加成聚合（加聚）反应。如果形成聚合物的反应涉及到在单体间消去小分子如水或醇，这样的反应就叫做缩合聚合（缩聚）反应。在加聚反应中，不饱和的或环状的分子互相反应，彼此增长，而且没有消去单体分子的任何一部分。那么，当然，聚合物的实验式与单体的相同。
Experimental(Preparation of Nylon6—10)
实验(制备尼龙6-10)
Place a solution of2.0ml.of sebacoyl chloride in100ml.of carbon tetrachloride in a 200-ml.tall-form beaker.Over the acid chloride solution carefully pour a solution of2.2g.
of liexamethylenediamine and1.5g.of sodium hydroxide in50ml.of water.The addition of the diamine-sodium hydroxide solution is best done by pouring the solution through a funnel placed so that its outlet is just over the surface of the diacid solution.Grasp the polymeric film which forms at the interface of the two solutions with forceps and raise it from the beaker as continuously forming rope.If a mechanical windup device is placed above the beaker,the polymer may be wound up continuously until one of the reactants is exhausted.
把2.0ml的氯代癸二酰溶解在100ml的四氯化碳中，然后放在200ml的高形烧杯中。（在200ml 的高形烧杯中，加入2.0ml的氯代癸二酰和100ml的四氯化碳）在氯代酸溶液上小心地倒入2.2克己二胺和1.5克氢氧化钠溶解于50ml水形成的溶液。己二胺和氢氧化钠的加入最好通过（容器上）放置的漏斗来进行，这样它的出口就正好在二元酸溶液的上方。用镊子抓住两种溶液界面的聚合物膜，作为连续形成的绳索状从烧杯中提出。如果在烧杯上装上机械上有发条的设备，聚合物就会被连续卷起，直到其中的一种反应物耗尽。
Wash the polymer thoroughly with water and finally with a50%acetone solution.Allow the washed poly
mer to air dry.Place about0.l g.of the dried polymer on a metal spatula or spoon and melt it carefully over a low flame care being taken not to char the polymer1. Touch a glass rod or a matchstick to the molten polymer and pull it slowly away to form a fiber.
先用水彻底地洗涤聚合物，最后用50%的丙酮溶液洗涤。然后把洗涤后的聚合物置于空气中干燥。把0.1克干燥的聚合物放在金属刮刀或金属勺上，在低温火焰上小心地使其熔化，当心不要使聚合物烧焦。用一根玻璃棒或火柴杆接触熔化的聚合物，然后慢慢地拉起来使其形成纤维。
24VOLUMETRIC ANALYSIS
24容量分析
Procedure
程序
Care must be exercised throughout the titration procedure3.The burette should be thoroughly cleaned with soap and water,rinsed with tap water,and finally,rinsed with distilled water.Just before use,the burette should be rinsed with two5-ml portions of the solution to be used in the burette.This is done by holding the burette in a semi-horizontal position and rolling the solution around the entire inner surface.
Allow the final rinsing to drain through the tip.
应该很小心整个滴定步骤的行使。这滴定管应该彻底地用肥皂和清水清洗，再用自来水冲洗，
最后用蒸馏水漂洗。只是在使用前，滴定管应该用两个5ml的北盛溶液润洗滴定管，将滴定管半水平放置，滚动滴定管，使溶液润洗滴定管内表面，最后让冲洗液从尖部缓慢流出。
Fill the burette to a point above the top marking and allow the solution to run out until the bottom of the meniscus is just at the top marking of the burette.The burette tip must be completely filled to deliver the volume measured.
将溶液装入滴定管刻度上方，使溶液流出，直到溶液的凹液面正好到滴定管顶部刻度线，这滴定管顶部必须完全地充满来供应着大量的测量。
In addition,the burette must be cleaned thoroughly after use because sodium hydroxide and other types of solutions will eventually frost the glass and render an expensive piece of equipment useless.
此外，滴定管必须彻底清洗后使用，因为氢氧化钠和其他类型的溶液混合，终究会霜化玻璃并致使一件昂贵的设备成为无用的。
26VAPOR-PHASE CHROMATOGRAPHY
26气相谱
In actual practice,a very small sample of the mixture is injected into a heated chamber where it is vaporized and swept through the column(which is encased in an oven which also is usually heated)with the aid of an inert carrier gas,most commonly helium.After the components of the mixture have been separated as they pass through the column, they pass through a detector located at the end of the column and are recorded as peaks on a mechanical recorder.A schematic diagram of a gas chromatograph is shown in Figure2.
实际操作中，将很少量的混合物试样注入加热室中，试样在此外气化，并在惰性载气d辅助下，通过谱柱，（谱柱通常被置于加热的烘箱或炉子内），混合物的组分通过谱柱实验分离后，通过位于谱柱末端的检测器，而且由机械的记录仪以峰的形式记录下来，气相谱仪的示意图如图2.
Figure2.Schematic diagram of a gas chromatograph.
图2。原理图的一种气相谱仪。
The time required for a compound to pass through a column is known as its retention time, which depends on many variables,including the following:
一个复合所需的时间通过柱是叫做停留时间，这取决于许多变量，包括以下几点:
1.The nature of the adsorbent.
1。吸附剂的性质。
2.The concentration of adsorbent in the inert solid support.
2。浓度的惰性固体吸附剂的支持。
3.The degree to which the compound being analyzed is adsorbed by adsorbent.
3。的程度进行了实证分析检验是由复合吸附剂吸附。
4.The volatility of the compound.
4。波动的化合物。
reactive翻译
5.The column temperature.
5。柱温。
6.The rate of flow of carrier gas.
6。流量气体载体。
7.The nature of the carrier gas.
7。载气的性质。
8.The dimensions of the column.
8。尺寸的专栏。
By suitable adjustments of these variables it is usually possible to effect a clean separation of all of the components of a mixture of compounds.
通过适当调整对这些变量通常是可能的分离效果干净所有的部件的混合的化合物。
The detector must be capable of measuring some difference between the carrier gas alone and the.'carrier gas mixed with-an effluent compound.Differences in thermal conductivity are easy to measure and provide a high sensitivity to detection.Thus,this type of detector is the one most frequentl
y used.Changes in the thermal conductivity of the effluent gases are sensed by the detector and relayed to a recorder by electronic means.The recorder provides a display of peaks as a function of time.Each peak represents a new compound that has passed through the detector.Furthermore,the area under each peak,when presents a measure of the amount of the compound present in the original mixture.
这个检测器必须能够测量出一些不同在单独的载气和伴随着流出的化合物的载气之间，在热传导性方面的不同之处很容易去测量并且它对于检查提供了一个高的灵敏度。另外，这种形式的检测器是最常使用的。流出气体的热传导性的变化被检测器检测并且通过电子的方法传播给记录器。记录仪就给出了峰随时间变化的函数。每个峰代表一个已经通过检测器的新的化合物。因此，每一个峰下面的面积，经过适当的校准，就代表了在原混合物中这个化合物
的量的一个量度。
27INFRARED SPECTROSCOPY
27红外光谱
Infrared spectroscopy is also used extensively for quantitative analysis of mixtures of organic compoun
ds.Within an accuracy of±1~5per cent,depending on the precautions employed in the determination,it is frequently possible to determine the percentage of each component in a mixture of two or more compounds.For example,one can readily determine the percentages of ortho,meta,and para isomers obtained by bromination of toluene in the presence of ferric bromide catalyst by the use of infrared spectroscopy.The chemical literature contains this and thousands of additional applications of the use of infrared spectroscopy in quantitative analysis.
红外光谱也广泛用于定量分析有机化合物的混合物的定量分析。精度在±1~5%范围内，它常常是可以测定的各组成部分的比例混合物中两种或两种以上的化合物。，该准确度取决于测量过程中操作的谨慎情况。例如，你能利用红外光谱容易地测量由甲苯在溴化铁催化作用下，溴化得到的邻位，间位，对位异构物的百分含量，化学文献包括这方面的应用和数千种在定量分析方面利用红外光谱的辅助和应用。
28NUCLEAR MAGNETIC RESONANCE(I)
28核磁共振(1)
When a proton is located in an external magnetic field,its magnetic moment can be aligned either with or against the external field.Since alignment with the field represents a more stable state than alignment against the field,energy must be supplied to flip the proton from the more stable to the less s
table alignment.The larger the external field,the greater the energy difference between nuclei aligned with or against the field.When nuclei are irradiated with electromagnetic radiation of an energy corresponding to the difference in energy between the two states,a transition or flip from one state to the other takes place.This is the nmr signal.
当一个质子位于外加磁场，它的磁矩能够被调整，无论它是随着还是对着这个外部领域。然而顺着这领域的代表比对着这领域的更加稳定的状态的调整，能量必须被提供来使质子从更

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