Organic Chemistry
IGCSE Chemistry Topic 11 16:50 English narration · English + 中文 subtitles burned in
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Petrol, plastic bottles, vinegar, alcohol, and the proteins in your body.
汽油、塑料瓶、醋、酒精，还有你体内的蛋白质。
They seem completely unrelated.
它们看起来毫不相关。
But every one of them is built from carbon.
但它们每一个都由碳构成。
Carbon is unique: it can bond to itself over and over, forming chains and rings of almost any length.
碳很独特：它能一次又一次地与自己成键， 形成几乎任意长度的链和环。
That one property gives us millions of compounds — and a whole branch of chemistry to organise them.
这一个特性给了我们数百万种化合物—— 以及整整一个化学分支来整理它们。
Welcome to organic chemistry.
欢迎来到有机化学。
Welcome to organic chemistry.
欢迎来到有机化学。
Homologous series, fuels, alkanes and alkenes, alcohols, acids, and polymers.
同系物、燃料、烷烃和烯烃、醇、酸，还有聚合物。
Let's begin.
让我们开始吧。
Before we name families, learn four ways to write an organic molecule.
在给家族命名之前，先学会四种书写有机分子的方法。
The molecular formula only shows how many of each atom there are — for ethane that is two carbons and six hydrogens.
分子式只显示每种原子有多少个—— 对乙烷来说就是两个碳和六个氢。
The displayed formula draws every atom and every bond in full, as in these pictures of methane, ethane and propane.
结构式把每个原子和每根键都完整画出来， 就像图中的甲烷、乙烷和丙烷。
The structural formula shows the arrangement without drawing every bond, for example three hydrogens on carbon, then two hydrogens on carbon, then O-H for ethanol.
结构简式显示原子如何排列，但不画每一根键， 例如乙醇是三个氢连在碳上，再两个氢连在碳上，再连一个羟基。
And the general formula works for a whole family: for alkanes it is C-n H-two-n-plus-two.
而通式适用于整个家族：烷烃的通式是碳恩氢二恩加二。
Exams love these four names — learn them cold.
考试很爱这四个名字——务必记牢。
Look at the alkane family step by step.
一步一步看烷烃家族。
Methane has one carbon, ethane has two, propane has three.
甲烷有一个碳，乙烷有两个，丙烷有三个。
Each next member differs by one C-H-two unit — that is the hallmark of a homologous series.
每一个下一个成员都多出一个亚甲基单元——这就是同系物的标志。
Members share the same general formula and similar chemical properties, but physical properties change gradually: as the chain grows, boiling point rises and the liquid becomes thicker.
成员有相同的通式和相似的化学性质，但物理性质会逐渐变化： 链变长时，沸点升高，液体也更黏稠。
Same chemistry, slow change in physics — that is the series idea.
化学性质相同，物理性质慢慢变—— 这就是同系物的核心。
Organic compounds come in families called homologous series.
有机化合物分成叫做同系物的家族。
Every member of a family shares the same functional group — the atoms that give it its chemical behaviour — and the same general formula, shown here.
同一家族的每个成员都有相同的官能团—— 赋予它化学性质的原子——以及相同的通式，如图所示。
Alkanes have only single carbon-carbon bonds.
烷烃只有碳碳单键。
Alkenes have a carbon-carbon double bond.
烯烃有碳碳双键。
Alcohols carry an O-H group, and carboxylic acids carry a C-O-O-H group.
醇带有羟基，羧酸带有羧基。
A compound with only single carbon-carbon bonds is saturated; a double bond makes it unsaturated.
只有碳碳单键的化合物是饱和的； 有双键就是不饱和的。
And the name tells you everything: the start gives the number of carbons, the ending gives the family.
名字告诉你一切：开头给出碳原子数，结尾给出所属家族。
Put the bond picture clearly.
把键的图景说清楚。
Ethane has a single carbon-carbon bond — only single bonds means saturated.
乙烷有碳碳单键——只有单键就是饱和的。
Ethene has a carbon-carbon double bond — any bond that is not single makes the molecule unsaturated.
乙烯有碳碳双键——只要有不是单键的键，分子就是不饱和的。
Saturated compounds are generally less reactive; the double bond in an unsaturated compound is a reactive spot that can open up.
饱和化合物一般不那么活泼；不饱和化合物中的双键是一个活泼点，可以打开。
Remember: saturated equals single bonds only; unsaturated equals a double bond somewhere.
记住：饱和等于只有单键；不饱和等于某处有双键。
Structural isomers share the same molecular formula but have different structural formulae — the atoms are connected differently.
同分异构体有相同的分子式，但结构简式不同——原子的连接方式不一样。
Take four carbons and ten hydrogens.
以四个碳和十个氢为例。
You can draw a straight chain of four carbons: that is butane.
你可以画一条四个碳的直链：那是丁烷。
Or you can branch: three carbons in a row and one carbon sticking off the middle — that is two-methylpropane.
也可以分支：三个碳排成一行，中间伸出一个碳——那是甲基丙烷。
Same atoms, same counts, different shape.
原子相同、个数相同，形状不同。
In an exam, if two names fit one formula, you are looking at isomers.
考试里如果两个名字对应同一个分子式， 你面对的就是同分异构体。
The end of the name tells the family: ane for an alkane, ene for an alkene, ol for an alcohol, and oic acid for a carboxylic acid.
名字的结尾告诉你所属家族：烷对应烷烃，烯对应烯烃，醇对应醇， 酸对应羧酸。
The start tells the carbon count: meth is one, eth is two, prop is three, but is four.
开头告诉你碳原子数：甲是一，乙是二，丙是三，丁是四。
For longer alkenes and alcohols, a number shows where the functional group sits.
对较长的烯烃和醇，数字标出官能团的位置。
But-one-ene has the double bond after the first carbon; but-two-ene has it after the second.
丁一烯的双键在第一个碳之后； 丁二位烯的双键在第二个碳之后。
Propan-one-ol and propan-two-ol place the O-H group on different carbons.
丙一醇和丙二位醇把羟基放在不同的碳上。
Count carefully, then write the number into the name.
仔细数碳，再把数字写进名字里。
The three fossil fuels are coal, natural gas, and petroleum — also called crude oil.
三种化石燃料是煤、天然气和石油——石油也叫原油。
Methane is the main part of natural gas.
甲烷是天然气的主要成分。
A hydrocarbon is a compound made of hydrogen and carbon only, and petroleum is a mixture of many different hydrocarbons.
碳氢化合物是只由氢和碳组成的化合物， 而石油是许多不同碳氢化合物的混合物。
An oil refinery, like the one in this photo, separates that mixture into useful fuels.
像照片中这样的炼油厂， 会把这种混合物分离成有用的燃料。
Remember the trio: coal, natural gas, petroleum — and that methane is the star of natural gas.
记住这三种：煤、天然气、石油—— 以及甲烷是天然气的主角。
Crude oil, or petroleum, is a mixture of many hydrocarbons — compounds of hydrogen and carbon only.
原油，或称石油，是许多碳氢化合物的混合物——只由氢和碳组成的化合物。
To separate them, we use fractional distillation.
要分离它们，我们用分馏。
The oil is heated and rises up a tall fractionating column, hot at the bottom and cool at the top.
油被加热，沿着一根高塔上升，塔底热、塔顶冷。
Each group of molecules turns back to liquid at a different height, giving us fractions.
每一组分子在不同的高度重新变成液体，得到馏分。
As you go up the column, the molecules get shorter, boil at lower temperatures, flow more easily, and catch fire more easily.
沿着塔往上走，分子变短、 沸点变低、流动更容易、也更容易着火。
Bitumen for roads stays at the hot bottom; refinery gas leaves the cool top.
修路用的沥青留在炽热的塔底； 炼厂气从凉爽的塔顶离开。
Learn what each fraction is for.
记住每个馏分的用途。
Refinery gas heats homes and cooks food.
炼厂气用于取暖和做饭。
Gasoline, or petrol, fuels cars.
汽油给汽车当燃料。
Naphtha is a raw material for making chemicals.
石脑油是制造化学品的原料。
Kerosene, also called paraffin, is jet fuel.
煤油也叫石蜡油，是喷气燃料。
Diesel oil runs diesel engines.
柴油驱动柴油发动机。
Fuel oil powers ships and home heating.
燃料油为轮船和家庭供热提供动力。
Lubricating oil makes lubricants, waxes and polishes.
润滑油用来做润滑剂、蜡和抛光剂。
Bitumen, the thickest at the bottom, makes roads.
最稠的沥青在塔底，用来铺路。
Match the name to the use — that is a classic exam question.
把名字和用途对上——这是经典考题。
From the hot bottom to the cool top, four trends run together.
从炽热的塔底到凉爽的塔顶，四条趋势一起变化。
Chain length gets shorter — smaller molecules.
链长变短——分子更小。
Volatility rises — they turn to gas more easily.
挥发性升高——更容易变成气体。
Boiling point falls.
沸点下降。
Viscosity falls — they flow more easily.
黏度下降——流动更容易。
So bitumen is long-chain, low volatility, high boiling point, high viscosity.
所以沥青是长链、低挥发、高沸点、高黏度。
Refinery gas is the opposite: short, very volatile, low boiling point, runny.
炼厂气正好相反： 短链、极易挥发、低沸点、很稀。
Link those four words: chain length, volatility, boiling point, viscosity.
把这四个词连起来：链长、挥发性、沸点、黏度。
Alkanes are saturated hydrocarbons — only single bonds.
烷烃是饱和碳氢化合物——只有单键。
They are generally unreactive, but you must know two reactions.
它们一般不活泼，但你必须知道两个反应。
First, combustion: burn an alkane in plenty of oxygen and you get carbon dioxide and water.
第一，燃烧：让烷烃在充足的氧气中燃烧，生成二氧化碳和水。
Second, substitution with chlorine, where one hydrogen atom is swapped for a chlorine atom.
第二，与氯的取代反应， 一个氢原子被一个氯原子替换。
But this only happens in ultraviolet light — the light supplies the activation energy.
但这只在紫外线下发生——光提供活化能。
That makes it a photochemical reaction.
这使它成为光化学反应。
Write the substitution equation carefully.
仔细写出取代反应方程式。
Methane plus chlorine gas gives chloromethane plus hydrogen chloride.
甲烷加氯气生成一氯甲烷和氯化氢。
One hydrogen atom is replaced by one chlorine atom — that is what substitution means.
一个氢原子被一个氯原子替换——这就是取代的含义。
It will not run in the dark: ultraviolet light is required, because the light provides the activation energy.
在黑暗中它不会发生： 需要紫外线，因为光提供活化能。
Call it a photochemical reaction and you have the exam phrase locked in.
把它叫做光化学反应，考试用语就锁住了。
Alkenes have a carbon-carbon double bond, which makes them unsaturated and much more reactive.
烯烃有碳碳双键，这使它们不饱和，也活泼得多。
That double bond can open up, so alkenes undergo addition reactions — two molecules join into one.
那个双键可以打开， 所以烯烃发生加成反应——两个分子结合成一个。
This gives us the classic test for unsaturation: shake the compound with orange bromine water.
这给了我们检验不饱和的经典方法： 把化合物与橙色的溴水一起振荡。
An alkene decolourises it — the orange disappears.
烯烃使它褪色——橙色消失。
An alkane leaves it orange.
烷烃则让它保持橙色。
Add hydrogen with a nickel catalyst and an alkene becomes an alkane; add steam with an acid catalyst and it becomes an alcohol.
加氢并用镍作催化剂，烯烃变成烷烃；加蒸汽并用酸作催化剂，它变成醇。
Zoom in on the bromine water test — it is almost guaranteed in papers.
仔细看溴水检验——试卷几乎必考。
Shake the unknown with orange bromine water.
把未知物与橙色溴水一起振荡。
If the orange fades to colourless, the compound is unsaturated: its carbon-carbon double bond reacted with the bromine in an addition reaction.
如果橙色褪成无色，化合物就是不饱和的：它的碳碳双键与溴发生了加成反应。
If the liquid stays orange, the compound is saturated — an alkane has no double bond to open.
如果液体保持橙色，化合物就是饱和的——烷烃没有可打开的双键。
Alkene decolourises; alkane does not.
烯烃使溴水褪色；烷烃不会。
Say that in one sentence and the mark is yours.
一句话说清，分数就是你的。
Long alkane molecules from crude oil are not very useful — but short ones are in high demand.
原油里的长链烷烃不太有用——但短链的需求很大。
Cracking solves this.
裂化解决了这个问题。
Heat a large alkane with a catalyst, and it breaks into a smaller alkane plus an alkene.
用催化剂加热一个大烷烃，它就断裂成一个较小的烷烃加一个烯烃。
Atoms are conserved, so you can always work out the missing product by subtracting.
原子守恒， 所以你总能用减法算出缺少的产物。
Cracking gives us petrol-sized molecules, hydrogen, and the alkenes we need to make plastics.
裂化给了我们汽油大小的分子、氢气， 以及制造塑料所需的烯烃。
Worked example.
例题。
Cracking one molecule of decane — ten carbons, twenty-two hydrogens — gives octane, eight carbons and eighteen hydrogens, and one other product.
裂化一个癸烷分子——十个碳、二十二个氢——得到辛烷，八个碳和十八个氢， 以及另一种产物。
Atoms are conserved, so subtract: carbon ten minus eight is two; hydrogen twenty-two minus eighteen is four.
原子守恒，所以做减法：碳十减八得二；氢二十二减十八得四。
The other product is two carbons and four hydrogens — ethene, an alkene, because it fits C-n H-two-n.
另一种产物是两个碳和四个氢——乙烯，一种烯烃，因为它符合碳恩氢二恩。
How do you tell the products apart?
如何区分这两种产物？
Shake each with orange bromine water: ethene decolourises it; octane is saturated and leaves it orange.
分别与橙色溴水振荡：乙烯使它褪色；辛烷是饱和的， 让它保持橙色。
Balance cracking equations by counting atoms; the alkene is whatever is left over.
用数原子的方法配平裂化方程式；烯烃就是剩下的那个。
Alcohols carry the O-H functional group, and the one to know is ethanol.
醇带有羟基官能团，要记住的是乙醇。
There are two ways to make it.
制造它有两种方法。
Fermentation: yeast turns glucose into ethanol and carbon dioxide, at about thirty degrees, without oxygen.
发酵：酵母在大约三十度、 无氧的条件下把葡萄糖变成乙醇和二氧化碳。
It uses renewable sugar, but it is slow and the ethanol is impure.
它使用可再生的糖，但很慢，而且乙醇不纯。
Or hydration: add steam to ethene at three hundred degrees and high pressure, with an acid catalyst.
或者水合：在三百度高压下用酸作催化剂给乙烯加蒸汽。
That is fast and gives pure ethanol, but it uses petroleum, which is not renewable.
这很快，得到纯乙醇， 但它使用不可再生的石油。
Ethanol burns well, so it is a fuel, and it dissolves many things, so it is a solvent.
乙醇燃烧良好，所以是燃料；它能溶解许多物质，所以是溶剂。
Compare the two routes side by side.
把两条路线并排比较。
Fermentation: yeast, about twenty-five to thirty-five degrees Celsius, no oxygen.
发酵：酵母，大约二十五到三十五摄氏度，无氧。
It turns glucose into ethanol and carbon dioxide.
它把葡萄糖变成乙醇和二氧化碳。
Plus: renewable sugar.
优点：可再生的糖。
Minus: slow, and the ethanol is impure.
缺点：慢，而且乙醇不纯。
Hydration of ethene: three hundred degrees, about sixty atmospheres, acid catalyst.
乙烯水合：三百度，大约六十个大气压，酸作催化剂。
Steam adds across the double bond.
蒸汽加到双键上。
Plus: fast and pure.
优点：快且纯。
Minus: ethene comes from petroleum, so it is not renewable.
缺点：乙烯来自石油，所以不可再生。
Exams love a table of conditions, advantages and disadvantages — build that table in your head.
考试很爱条件、优点和缺点的表格—— 在脑中建好那张表。
Carboxylic acids carry the C-O-O-H group, and ethanoic acid is the one to know — it is what makes vinegar sour.
羧酸带有羧基，要记住的是乙酸——它让醋变酸。
Like any acid, it reacts with metals to give a salt and hydrogen, with bases to give a salt and water, and with carbonates to give a salt, water and carbon dioxide.
像任何酸一样， 它与金属反应生成盐和氢气，与碱反应生成盐和水，与碳酸盐反应生成盐、水和二氧化碳。
Its salts are called ethanoates.
它的盐叫做乙酸盐。
You can make ethanoic acid by the oxidation of ethanol, with acidified potassium manganate seven, or by bacteria as vinegar is made.
你可以通过氧化乙醇来制造乙酸—— 用酸化的高锰酸钾，或者像酿醋那样让细菌来做。
And here is the useful one: a carboxylic acid plus an alcohol, with an acid catalyst, makes an ester plus water.
还有一个有用的反应： 羧酸加醇，用酸作催化剂，生成酯加水。
Name it from its parents — the alcohol gives the first part, the acid gives the second.
用它的来源命名——醇给出第一部分， 酸给出第二部分。
Ethanoic acid can be made by oxidising ethanol.
乙酸可以通过氧化乙醇来制造。
In the lab you use acidified potassium manganate seven — a strong oxidising agent that turns ethanol into ethanoic acid.
在实验室里用酸化的高锰酸钾——一种强氧化剂， 把乙醇变成乙酸。
In industry and in the kitchen, bacteria do a similar job during the making of vinegar.
在工业和厨房里，细菌在酿造醋的过程中做类似的事。
So ethanol can go two ways: burn as a fuel, or oxidise to the acid that makes vinegar taste sharp.
所以乙醇可以走两条路：当作燃料燃烧，或者氧化成让醋变酸的酸。
Name the ester from its two parents.
用它的两个来源给酯命名。
Ethanol plus ethanoic acid, with an acid catalyst, gives ethyl ethanoate plus water.
乙醇加乙酸，用酸作催化剂，生成乙酸乙酯加水。
The ester functional group is the carbon-oxygen double bond next to a carbon-oxygen single bond in the middle of the chain.
酯的官能团是链中间的碳氧双键旁边连着一个碳氧单键。
The alcohol supplies the first part with an yl ending — ethyl.
醇给出带有基结尾的第一部分——乙基。
The acid supplies the second part with an oate ending — ethanoate.
酸给出带有酸根结尾的第二部分——乙酸根。
So ethanol and ethanoic acid make ethyl ethanoate.
所以乙醇和乙酸生成乙酸乙酯。
Always alcohol first, acid second.
永远是醇在前，酸在后。
A polymer is a giant molecule built from many small ones called monomers.
聚合物是由许多叫做单体的小分子构建的巨大分子。
In addition polymerisation, unsaturated monomers join together and nothing else is produced.
在加聚反应中， 不饱和的单体连接在一起，不产生其他任何东西。
Watch the carbon-carbon double bonds open up: each ethene monomer links to the next, building a long chain of poly(ethene).
看碳碳双键打开： 每个乙烯单体连到下一个，构建出长长的聚乙烯链。
The small part that repeats along the chain is called the repeat unit, and we draw it in brackets.
沿链重复的那个小部分叫做重复单元， 我们用括号把它画出来。
No other product — that is what makes it addition.
没有其他产物——这就是加聚的特点。
Look at the diagram.
看这张图。
Many ethene monomers start with a carbon-carbon double bond.
许多乙烯单体一开始都有碳碳双键。
In addition polymerisation those double bonds open, and the carbons link into a long single-bonded chain — poly(ethene).
在加聚中那些双键打开， 碳原子连成一条长的单键链——聚乙烯。
The repeat unit is the small piece that keeps appearing; we draw it inside square brackets with a subscript n for many copies.
重复单元是不断出现的那一小段； 我们把它画在方括号里，右下角加一个恩表示许多份。
No water, no hydrogen chloride, no second product at all.
没有水、没有氯化氢、 完全没有第二种产物。
If the only product is the polymer, you are looking at addition polymerisation.
如果唯一产物就是聚合物，你看到的就是加聚。
The other kind is condensation polymerisation.
另一种是缩聚。
Here the monomers join, but a small molecule — usually water — is lost each time a bond forms.
这里单体连接起来，但每形成一个键就失去一个小分子——通常是水。
Two types matter.
有两种类型很重要。
Polyamides, like nylon, are made from a dicarboxylic acid and a diamine, joined by an amide linkage.
聚酰胺，比如尼龙，由二元羧酸和二元胺制成，用酰胺键连接。
Polyesters, like PET, are made from a dicarboxylic acid and a diol, joined by an ester linkage.
聚酯，比如涤纶，由二元羧酸和二元醇制成，用酯键连接。
Proteins are natural polyamides, built from amino acids.
蛋白质是天然的聚酰胺， 由氨基酸构建。
But there is a cost: most plastics do not break down, so they fill landfill, pollute the oceans, and give off toxic gases if burned.
但这有代价：大多数塑料不会降解，所以它们填满垃圾填埋场、 污染海洋，燃烧时还放出有毒气体。
The new bond that joins the monomers is the linkage.
连接单体的新键叫做键合。
In a polyamide such as nylon, the linkage is an amide link: carbon double-bonded to oxygen, then bonded to nitrogen with a hydrogen — written C-O N-H.
在尼龙这样的聚酰胺中，键合是酰胺键： 碳与氧双键相连，再与带氢的氮相连。
In a polyester such as PET, the linkage is an ester link: carbon double-bonded to oxygen, then single-bonded to another oxygen — C-O O.
在涤纶这样的聚酯中，键合是酯键： 碳与氧双键相连，再与另一个氧单键相连。
Exams often show a repeat unit in brackets and ask you to circle the linkage.
考试常画出括号里的重复单元， 让你圈出键合。
Find the C-O next to N-H for amide, or the C-O next to O for ester.
酰胺找碳氧旁的氮氢，酯找碳氧旁的氧。
PET can also be broken back into its monomers and remade — that is recycling of a polyester.
涤纶还可以拆回单体再重新制造——那就是聚酯的回收。
Proteins are natural polyamides.
蛋白质是天然的聚酰胺。
Their monomers are amino acids — small molecules that each carry both an amine group and a carboxylic acid group.
它们的单体是氨基酸——每个小分子都同时带有胺基和羧基。
When amino acids join, water is lost and an amide linkage forms, just as in nylon.
氨基酸连接时失去水，形成酰胺键，就像尼龙一样。
So a protein chain is a long polyamide built by condensation.
所以蛋白质链是缩聚构建的长聚酰胺。
Nature and the nylon factory use the same idea: link monomers, lose water, grow a chain.
自然界和尼龙工厂用的是同一个思路：连接单体、失去水、长出一条链。
Plastics are made from polymers.
塑料由聚合物制成。
Because many plastics do not break down, waste is a serious problem.
因为许多塑料不会降解，废弃物是个严重问题。
They build up in landfill sites for hundreds of years.
它们在垃圾填埋场堆积数百年。
They collect on beaches and in the oceans and harm sea life.
它们聚集在海滩和海洋中，伤害海洋生物。
Burning them can release toxic gases.
燃烧它们会放出有毒气体。
Most plastics are non-biodegradable — that single fact drives the pollution you see in this photograph.
大多数塑料不可生物降解——正是这一事实 造成了照片中的污染。
Reduce, reuse, recycle, and know why addition plastics last so long: their chains do not fall apart easily.
减少使用、重复使用、回收利用，并明白为什么加聚塑料如此持久： 它们的链不容易断开。
Three marks to lock in.
锁住三个分。
First: learn each homologous series by its functional group and general formula.
第一：按官能团和通式记住每个同系物家族。
Second: the bromine water test — an alkene turns orange bromine water colourless, an alkane leaves it orange.
第二：溴水检验—— 烯烃使橙色溴水褪色，烷烃让它保持橙色。
Third: addition polymerisation joins unsaturated monomers with no other product, while condensation polymerisation loses a small molecule, usually water, each time.
第三：加聚把不饱和单体连接起来， 不产生其他产物；而缩聚每次都失去一个小分子，通常是水。
Master these, and this topic is yours.
掌握这些，这个专题就是你的了。